Silba adipata McAlpine

 


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Black Fig Fly

 

 

 

The present page contains a compilation of my posts on the Ourfigs.com forum (sticky topic devoted to the Blak Fig Fly), grouped by themes.

It also constitutes an English written synthesis of the main informations contained in the website (in which the texts are in French).

 

SUMMARY

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ATTACKS SYMPTOMS

IDENTIFYING THE BLACK FIG FLY

DETECTING THE BLACK FIG FLY

ATTACKS CHARACTERISTICS

ATTACKS  OBSERVATIONS OVER THE SEASON

EGGS LAYING ACTIVITY

FEEDING ACTIVITY

FIGS INFESTATION

POSSIBLE CONFUSION WITH A PATHOGENIC FUNGI ATTACK

LIFE CYCLE DURATION / LIFE SPAN

MATING

LARVA

PUPA

CONTROL METHODS

 

ATTACKS SYMPTOMS

 

BLACK FIG FLY ATTACKS SYMPTOMS

Hereafter, the main symptoms of the Black Fig Fly attack...(more details in the specific page).
 

Black Fig Fly (Silba adipata McAlpine) : attack symptoms.

 

Black Fig Fly (Silba adipata McAlpine) : attack symptoms.

 

Black Fig Fly (Silba adipata McAlpine) : attack symptoms.

 

Black Fig Fly (Silba adipata McAlpine) : attack symptoms.

 

Black Fig Fly (Silba adipata McAlpine) : attack symptoms.

 

Black Fig Fly (Silba adipata McAlpine) : attack symptoms.

 

Black Fig Fly (Silba adipata McAlpine) : attack symptoms.

 

Black Fig Fly (Silba adipata McAlpine) : attack symptoms.

 

SYMPTOMS SPECIFICITY DEPENDING ON THE SKIN COLOR

According to my observations, when the small green unripe figs are infested by the Blak Fig Fly, they turn purplish red if they belong to a dark-skinned variety (photograph 1), while they remain entirely green if they belong to a light-skinned variety (photograph 2).

Light-skinned and dark-skinned refer to the skin color at the maturity stage (light-skinned : green or yellow ; dark-skinned : all the other colors, including bronze).
 

Black Fig Fly (Silba adipata McAlpine) : attack symptoms.

 

Black Fig Fly (Silba adipata McAlpine) : attack symptoms.

Note : photograph 2 credited to Bernard PEYRE.

 

A SYMPTOM EXCEPTION FOR DARK-SKINNED FIGS

Sometimes, in very rare cases (one to two figs in the crop), We can observe exceptions for the dark-skinned varieties : the unripe green fig remains entirely green for a very long period after the eggs-laying (including the abandonment of the fig by the larvae, therefore the appearence of the exit holes).

See below, examples of a breba crop fig of the 'Dauphine' variety (photograph 1), or of the 'Grise de la Saint-Jean' variety (photograph 2), and of a fig of the uniferous variety 'Bourjassote Noire' (photograph 3).
 

Black Fig Fly (Silba adipata McAlpine) : larvae exit holes.

 

Black Fig Fly (Silba adipata McAlpine) : larva exit hole.

 

Black Fig Fly (Silba adipata McAlpine) : larva exit hole.

Note : photograph 1 credited to Bernard PEYRE ; photograph 3 credited to Margaux ALLIX.

 

POSSIBLE CONFUSION BETWEEN FIGS PHYSIOLOGICAL DROP AND BLACK FIG FLY ATTACKS

Figs physiological drop.

It is common to find on a fig tree branch one or several tiny more or less reddened unripe figs, which finally fall to the ground, but which are not attacked by Silba adipata McAlpine.

Their fall is linked only to the physiology of the tree, and is called "physiological drop".

The causal factors of the figs physiological drop are the occurrence of late spring frosts, sudden temperature variations over a short period, significant variations in temperature between day and night, long periods of strong wind, heatstroke (short episodes of hot wind ...), unfavorable growing conditions such as lack of water.

For breba figs (first crop of biferous varieties), the main factor responsible for the physiological drop is the non-satisfaction of the variety's needs in terms of number of winter cold days. In this case, the physiological drop is massive, often wiping out almost the entire breba crop.

Most reddened unripe figs involved in physiological drop are very small (less than 1 cm in diameter). But it should be noted that some of them have a diameter of up to 1.5 cm, which therefore exceeds that of the critical size for the attack of Silba adipata McAlpine (1.1 cm, according to my observations). And in the case of physiological drop affecting breba figs, the diameter can greatly exceed 1.5 cm.

Below, two photographs showing reddened unripe figs involved in the physiological drop, isolated (photograph 1) or in a group (photograph 2).
 

Isolated reddening unripe fig involved in the physiological drop.

 

Group of reddening unripe figs involved in the physiological drop.
 

Below, two photographs showing tiny reddening unripe figs that have been removed from the tree before their physiological drop (the same, whole then cut in half).

None of them have been attacked by the Black Fig Fly.

The largest of these figs (on the top in the photograph 1) has a diameter of only 1.3 cm. But this diameter and that of four others equal or exceed the minimal diameter for the Black Fig Fly attack that I observed (1.1 cm).

Note in the photograph 2 the more or less dark brown interior that may induce with the naked eye a doubt about the absence of a Silba adipata McAlpine attack.
 

Tiny reddening unripe figs removed from the tree before their physiological drop.

 

Tiny reddening unripe figs removed from the tree before their physiological drop.
 

Possbile confusion with Black Fig Fly attacks.

The external appearance of an unripe fig involved in the physiological drop is strictly identical to that of an unripe fig attacked by Silba adipata McAlpine (unless at least one larva has already abandoned the attacked fig, in which case there is at least one larva exit hole in the skin).

And there is an overlap between the diameters of these two types of reddened unripe figs falling to the ground.

For these two reasons, a confusion is possible between them.

Avoiding the confusion.

First, we must keep in mind that the figs physiological drop phenomenon exists, and that the concerned figs should not be confused with figs attacked by Silba adipata McAlpine.

Secondly, in the case of a reddened unripe fig not showing larvae exit holes, the fig must be opened in search of signs of Silba adipata McAlpine attack, in the inflorescence and possibly in the parenchyma. It is the absence of traces of attack inside the fig that leads to the conclusion that it is concerned by the physiological drop.

But, in my experience, in many cases it is not easy to determine with the naked eye the absence of traces of Silba adipata McAlpine attack, due to the more or less dark brown interior.

Identification difficulties

In the tiny figs involved in the physiological drop, the hollow interior is lined with a barely perceptible growing inflorescence that appears more as a villus with the naked eye.

In some figs, it is pure white, which leads to the conclusion that there is no Silba adipata McAlpine attack. But most often the interior takes a more or less dark brown tint, extended over the entire central cavity surface, or irregularly distributed over it, which leads to a doubt with the naked eye.

To be sure that the fig is concerned by the physiological drop, we must use a strong magnifier, or take a close-up photograph, in order to check that the brown short young inflorescence is not altered by larvae bites, in particular that the tips of the flowers styles are intact, not showing a localized dark brown or blackish color.

If the doubt remains, and it happened to me, the use of a stereomicroscope is imperative to verify the possible presence of one or more chorions (empty eggs envelopes) under the ostiolar scales, or in the ostiolar canal.

Below, two photographs showing the brown interior of reddened unripe figs concerned by the physiological drop.
 

Brown interior of a reddened unripe fig concerned by the physiological drop.

 

Brown interior of a reddened unripe fig concerned by the physiological drop.
 

Below, two photographic enlargements showing the interior of reddened unripe figs, and leading to the conclusion that these figs are involved in the physiological drop.

Photograph 1 : the young inflorescence is white and safe, despite the presence of brown spots near the fig neck.

Photograph 2 : the slightly brown flowers styles tips are intact.
 

White and intact inflorescence of a reddened unripe fig (physiological drop).

 

Slightly brown flowers styles tips not altered by larvae bites (physiological drop).

 

Retour début article Summary

 

IDENTIFYING THE BLACK FIG FLY

 

BLACK FIG FLY APPEARANCE IN CALIFORNIA (2021)

The presence of the Black Fig Fly in California is a sad new.

Here (eastern French Mediterarnean coast, near Toulon), we have been struggling with this major fig pest for 10 years ... No miracle solution.

This species is present in our region since one century, and it was not very active. But the last 10 years, its nuisance has continually increased.

Do not lose hope : it has a very strange behavior and according to the various places in a given region and to the fig tree varieties, its action can be moderate.

If you need to know more about the Black Fig Fly, you can consult the original version of the present website, entirely devoted to this species - Many photographs and videos. Texts in French.
 

Below two photograhs showing the Black Fig Fly (Silba adipata McAlpine).

Photograph 1 : Silba adipata McAlpine laying eggs under an unripe fig ostiolar scale.

Photograph 2 : Silba adipata McAlpine attacks the unripe figs.
 

Black Fig Fly (Silba adipata McAlpine) laying eggs under an unripe fig ostiolar scale.

 

The Black Fig Fly (Silba adipata McAlpine) attacks the unripe figs.

 

TWO PHOTOGRAPHS TO FAMILIARIZE US WITH THE BLACK FIG FLY

Just two photographs to familiarize us with the Black Fig Fly (Silba adipata McAlpine,1956) - More details in the general description page of the present website.

I must mention for those who are searching for documentation about this species that in all documents prior to 1956, the Black Fig Fly is known as Lonchaea aristella Beck. - so it is important to successively launch the Internet requests with the two Latin names.

If you read Italian, do not miss the major study (morphology, biology, fig infestation...) of the Black Fig Fly published in 1917 by Filippo SILVESTRI (1873- 1949), entomology professor at the university of Roma and director of an agrarian zoology institute near Napoli.

Reference : SILVESTRI F., 1917, Sulla Lonchaea aristella Beck. (Diptera : Lonchaeidae) dannosa alle infiorescenze e fruttescenze del caprifico e del fico, Bollettino del Laboratorio di Zoologia Agraria in Portici, vol.12, pp. 123 -146

Below, the first photograph shows a male specimen, recognizable by the apex (terminalia) of the abdomen. The second photograph shows a female specimen, the end of the abdomen of which is not really visible, but recognizable by the wide interocular space (the one for the male being narrow).
 

Black Fig Fly (Silba adipata McAlpine) : male specimen.

 

Black Fig Fly (Silba adipata McAlpine) : female specimen.

 

IDENTIFYING THE BLACK FIG FLY

Below, two photographs showing three black fig flies consuming latex on a green fig tree twig of the year.

We can note that the photographs allow lateral, dorsal and three-quarter views of the Black Fig Fly.

Characters to keep in mind : very small size (to be compared to that of the attachment point of the torn leaf petiole), uniform black color, brick red eyes, stocky appearance, wings position (closed and overlapping).
 

Three black fig flies consuming latex on a green fig tree twig of the year.

 

Three black fig flies consuming latex on a green fig tree twig of the year.

 

BLACK FIG FLY FEMALE OVIPOSITOR

According to my observations, it is very rare to see on the fig tree a female with the ovipositor out, when it is not laying eggs.

But the female exteriorizes almost always the ovipositor before dying (when captured in a trap, for instance).

This particularity makes easy the count of the females (ovipositor out) and the males (no visible ovipositor), when emptying the traps as part of a field experimentation. But this method is slightly approximate, because a very small part of the females do not release their ovipositor when dying. I did not precisely assess their proportion, but I think that it does not exceed 5 %.

Below, a photograph showing a female with the ovipositor out.
 

Black Fig Fly (Silba adipata McAlpine) female, with the ovipositor out.

 

BLACK FIG FLY SIZE

According to my observations and measurements, the common size (for the body, wings excluded) of the Black Fig Fly is 4 mm, but it exists a size variability for both sexes.

The female length (ovipositor excluded) varies from 3.5 to 5 mm. The length is often 4 mm, but the lengths of 3.5 mm and 5 mm are rather frequent.

The male length varies from 3.5 to 4.5 mm. The length is often 4 mm, but the length of 3.5 mm is frequent (that of 4.5 mm is not frequent). I found males with a length of 5 mm but they are very rare.

Note 1 : As it exists an overlap between the male and the female lengths, the size cannot be used to differentiate the sexes for the Silba adipata McAlpine species (the two differentiation criteria are the end of the abdomen and the interocular space - wide for the female and narrow for the male).

Note 2 : the size of Silba adipata McAlpine is more or less the twice of that of Drosophila suzukii Matsumura (Spotted Wing Drosophila).

Below, the photograph shows the common size for both sexes of the Black Fig Fly (4 mm).
 


 

The following photograph shows the 3 sizes that can be observed for the female Black Fig Fly (from the bottom to the top) : 5 mm, 3.5 mm, 4 mm (2 females).
 

 

Specimens with a length of 5 mm.

Photograph 1 : female specimen. Less frequent that the 4 mm long specimens, but not rare.
 

Black Fig Fly (Silba adipata McAlpine) : a 5 mm long female specimen.
 

Photograph 2 : male specimen (very rare) - note the end of the abdomen. I only captured two male specimens of this length.
 

Black Fig Fly (Silba adipata McAlpine) : a 5 mm long male specimen.

 

Male and female specimens with lengths of 3.5 mm and 4 mm.

Photograh1 : two male specimens (on the left : 4.2 mm ; on the right : 3.5 mm).
 

Black Fig Fly (Silba adipata McAlpine) : two male specimens.
 

Photograh 2 : three female specimens (on the right : 4 mm ; on the left : 3.5 mm).
 

Black Fig Fly (Silba adipata McAlpine) : three female specimens.

 

DISTINGUISHING SILBA ADIPATA McALPINE MALE AND FEMALE

Beyond the anatomical knowledge of the species, knowing how to recognize the male and the female presents many practical interests.

This was useful for me when studying the size variability, and for observing the precocity of the male individuals for the emergence out of the pupae.

This also made it possible to search for any specific attitudes depending on the sex when individuals of the species mutually push back, when one of them shows an aggressive behavior, or during mating.

And this allowed me flies population observations : male / female ratio for individuals concomitantly frequenting a fig tree ; count of feeding females on the fig tree during the intense eggs-layings period in the season, to compare their number with that of eggs laying ones.

The size is not a sex distinguishing criterion for Silba adipata McAlpine.

According to my measurements, the male has a size of 3.5 to 4 mm (or a little more, exceptionally 5 mm), while the common size of the female is 4 mm, with, in a minority but not rare way, a maximum size of 5 mm and a minimum size of 3.5 mm.

Thus, due to the sizes overlap between males and females, the size of the Silba adipata McAlpine individuals does not make it possible to distinguish males and females.

Two anatomical characteristics allow to recognize male and female for Silba adipata McAlpine : the abdomen end and the interocular space.

The abdomen end.

For the female : narrow segmentation ; wide orifice with the ovipositor tip slightly protuding.

For the male : last visible segment very developped ; below it, presence of the terminalia, which is a rather complex structure containing the copulatory organ.

Below, two photographs illustrating the abdomen end difference between a female (photograh 1) and a male (photograph 2).
 

Black Fig Fly female specimen.

 

Black Fig Fly male specimen.
 

Below, two photographs illustrating the abdomen end difference between a female (photograh 1) and a male (photograph 2) - ventral views.
 

Black Fig Fly female specimen (ventral view).

 

Black Fig Fly male specimen (ventral view).
 

The interocular space.

I observed that the interocular space of the male is significantly narrower than that of the female.

In this, I confirm the observations which have been published in 1934 by Eugène SÉGUY.

Reference : SÉGUY E. - Diptères (Brachycères), Faune de France, vol. 28, page 176, Paul LECHEVALIER et fils, Paris, 1934.

Below, two photographs illustrating the interocular space difference between a female (photograh 1) and a male (photograph 2).
 

Black Fig Fly : wide interocular space of the female.

 

Black Fig Fly : narrow interocular space of the male.
 

Note.

Determination of males and females by the abdomen end or by the interocular space width is impossible to achieve with the naked eye, or even with an ordinary magnifier, due to the tiny size of Silba adipata McAlpine.

But this is possible for me with the highly magnifying part of my manual bifocal magnifier, and this is easy with photographic and video enlargements or close-ups. And, of course, when using a stereomicroscope.
 

Examples.

Below, four examples of the use of both sex determination criteria for simultaneously identified black fig flies

Photograph 1 : two Black Fig Fly males, recognizable one by its interocular space and the other by its abdomen end.
 

Two Black Fig Fly males.
 

Below, photograph 2 : two Black Fig Fly females, recognizable one by its interocular space and the other by its abdomen end.
 

Two Black Fig Fly females.
 

Below, photograph 3 : two black fig flies, a male (recognizable by its interocular space) and a female (recognizable by its abdomen end).
 

Two black fig flies (a male and a female).
 

Below, photograph 4 : three black fig flies, a male (recognizable by its abdomen end) and two females (recognizable by their interocular space).
 

Three black fig flies (a male and two females).

 

POSSIBLE CONFUSION WITH LAMPROLONCHAEA SMARAGDI  WALKER, 1849 

A little-known fly is usually present in areas where the Black Fig Fly has been detected, and it lays eggs in the ripe figs (but with negligible effect on the crop).

Its name is Lamprolonchaea smaragdi Walker, 1849. And it belongs to the same family like that of Silba adipata McAlpine, 1956 (Lonchaeidae).

It has strictly the same flight pattern, strictly identical morphological characters, and the same wings venation (common to all species of the Lonchaeidae family).

But this species is generally clearly smaller than Silba adipata McAlpine (with exceptions…), and the metallic emerald green color of its thorax and its abdomen makes it possible to identify it (not without difficulties…).

I have noticed that, in direct sunlight and depending on the light incidence, the abdomen may appear golden in color (in part or in whole).

According to Eugène SÉGUY, who described the species under the synonym Lonchaea aurea Macquart, 1851 : " The larva especially develops in fruits already attacked by the medfly (oranges, figs) or by the codling moth (pears, plums, peaches) ; it is a secondary fruits destructive agent, which hastens their decomposition and favors their invasion by Drosophila ".

Reference : Diptera (Brachycères), Faune de France, E. SÉGUY, 1934, vol. 28, page 178, Paul LECHEVALIER et fils, Paris.

I noted that Eugène SÉGUY indicated (already in 1934...) that the species was reported in my region (Var French department), as well as in Corsica.

This species is present in my orchard, and I capture every year a few individuals (never more than 10, contrary to certain spots where they are very numerous in the traps).

But, I have never been able to observe a living individual, neither on fig trees, nor on other fruit trees. I did not identify any either in the thousands of photographs that I made in the field studying Silba adipata McAlpine, in some of which it could have appeared, after having visually escaped me.

And I did not detect any Lamprolonchaea smaragdi Walker individuals from attacked figs I placed in emergence boxes, in large scale when I was practicing black fig flies breeding.

Below, two photographs showing Lamprolonchaea smaragdi Walker individuals.
 

Lamprolonchaea smaragdi Walker, 1849.

 

Lamprolonchaea smaragdi Walker, 1849.
 

Below, two photographs of a Lamprolonchaea smaragdi Walker individual on the surface of a cup of clear water, where it was transferred from the trap to be observed and photographed under better conditions.

Photograph 1 : favorable light conditions reveal the metallic green color of the Lamprolonchaea smaragdi Walker's thorax and abdomen.

Photograph 2 : under a certain light incidence, Lamprolonchaea smaragdi Walker seems to have a golden abdomen.

Note : the photograph 2 shows the wing venation common to all Lonchaeidae family species.
 

Lamprolonchaea smaragdi Walker, 1849.

 

Lamprolonchaea smaragdi Walker, 1849.
 

Lamprolonchaea smaragdi Walker identification difficulties.

I have noticed that a Lamprolonchaea smaragdi Walker individual only reveals its emerald green color when viewed with high light intensity and favorable light incidence.

Without these light conditions, it appears of a black color, like Silba adipata McAlpine (to the naked eye, as in the photographs).

Suitable light conditions are rather easy to obtain, in direct sunlight and by examining the dead individual, rotating it in all directions with a tweezer to find the correct light incidence (preferably using a magnifier, but sometimes with the naked eye).

Two clues must be kept in mind to trigger a Lamprolonchaea smaragdi Walker identification, if the green color is not immediatly visible.

First, the individual looks like an abnormally small black fig fly.

Secondly, in direct sunlight, its black color is intensely bright on the surface of the trap liquid, drawing attention compared to all the other flies, including black fig flies.

Below, two photographs showing the difficulty of detecting the characteristic green color of Lamprolonchaea smaragdi Walker.

Photograph 1 : due to light conditions, the green color of the Lamprolonchaea smaragdi Walker individual is barely visible (note that there are no morphological differences with the Black Fig Fly).

Photograph 2 : a Lamprolonchaea smaragdi Walker individual compared to two black fig flies - the size difference is clearly visble, but the green color and the specific shine of Lamprolonchaea smaragdi Walker are not visible (due to the light conditions, although the photograph is not particularly dark).
 

Lamprolonchaea smaragdi Walker, 1849.

 

A lamprolonchaea smaragdi Walker individual compared to two black fig flies.

 

NYCTIA HALTERATA PANZER : A SECOND BLACK FIG FLY LOOK-ALIKE

I have met many times on fig trees, in different places, a small black fly which does not attack figs but which, according to my experience, can lead to a confusion with Silba adipata McAlpine for people who have never seen the latter.

It is Nyctia halterata Panzer, belonging to the Sarcophagidae family.

This fly does not lay eggs in the figs, but it can be observed moving on the fig tree leaves and on the figs.

The first difference with Silba adipata McAlpine is that it exclusively stays on the upper side of the leaves. It is never found on the underside of the fig tree leaves, which is the Silba adipata McAlpine privileged place of residence.

In fact, it is slightly larger than Silba adipata McAlpine, it moves clearly faster, and unlike it, it keeps its wings apart while walking.

Its abdomen appears longer and has long hairs at its end.

Its wings with pronounced black veins are partially smoky, while those of the Black Fig Fly are more finely ribbed and are uniformly translucent.

I occasionally catch a Nyctia halterata Panzer individual in my traps, but this species is more frequently visible on the fig tree than in them.

Below, three photographs showing Nyctia halterata Panzer on a fig tree leaf.
 

Nyctia halterata Panzer on a fig tree leaf.

 

Nyctia halterata Panzer on a fig tree leaf.

 

Nyctia halterata Panzer on a fig tree leaf.

 

THE THIRD BLACK FIG FLY LOOK-ALIKE

I previously dealt with two of the three main Black Fig Fly look-alikes I have observed : Lamprolonchaea smaragdi Walker and Nyctia halterata Panzer.

I present below the third of theses.

I have never observed this entirely black look-alike fly on a fig tree, both with the naked eye and among the thousands of photographs taken over many years. But, I regularly catch individuals of this species in my traps placed on fig trees, more or less numerous depending on the year.

I deduce that this species is in no way attracted to the Fig tree (leaves, current-year wood, latex, ripe figs), and is found in the traps only because it is attracted to the liquid bait. As it is the case with the olive fly, of which I regularly catch many specimens in my traps, having never observed an individual of this species on a fig tree.

Below, a photograph which compares the look-alike species with the Black Fig Fly (credit : Fabian COUSINIÉ, who is one of the contributors to the present website).

We note that the venation of the wing anterior edge of the look-alike species (on the right in the photograph) is different from that of the Black Fig Fly.
 

Unidentified look-alike species.
 

The usual size of the look-alike species is a body length of 5 mm. But on a few occasions I have found in the traps smaller individuals (body length : 4 mm). According to my observations, they are males, but I do not have a sufficient number of observations to say that this is always the case.

We note that there is an overlap with the Silba adipata McAlpine size (common body length 4 mm, and a females minority part with a body length of 5 mm).

Below, a photograph showing two individuals of the look-alike species, respectively of a 5 mm and 4 mm length.
 

Two specimens of the unidentified look-alike species, with a different size.
 

Below, a photograph showing a male specimen of the look-alike species 4 mm long, smaller than the common size (5 mm).
 

A male specimen of the unidentified look-alike species.

The main criterion allowing to distinguish the look-alike species from Silba adipata McAlpine is the venation of the wing anterior edge.

To observe the wing venation, it is necessary to use a strong magnifier and examine the deployed wing flat on the surface of the liquid contained in the trap, or of clear water in a cup.

Below, two photographs which allow the comparison of the venation of the Black Fig Fly wing anterior edge with that of the look-alike species.

In the first photograph (Black Fig Fly), we note that the venation of the wing anterior edge is that of the Lonchaeidae family, to which this species belongs.

The subcosta (Sc) runs very closely and almost in parallel with the radius (R1) and joins the costa (C) a little forward than R1 seems to do. In fact, R1 dives towards C without touching it and follows it very closely, gradually approaching to die far enough from the point of junction of Sc with C.

This is more visible on the left wing in the photograph.

It should be emphasized that, being common to all genera and species of the Lonchaeidae family, the venation of the wing anterior edge does not identify Silba adipata McAlpine.

But it can be used to rule out look-alike species which would present a different configuration. The presence of the wing anterior edge configuration of the Lonchaeidae family is a necessary (but not sufficient) condition, which must imperatively be verified during the identification process of Silba adipata McAlpine.
 

Black Fig Fly wing venation.
 

In the second photograph (look-alike species), we note that the venation of the wing anterior edge is not that of the Lonchaeidae family.

In fact, the subcosta clearly diverges from the radius to join the costa much forward than it is the case for the Black Fig Fly.

I also note that the subcosta is thiner than the radius, and that the subcosta curve is not regular.
 

Wing venation of the unidentified look-alike species.
 

There is, like for Silba adipata McAlpine, a costal break just before the junction of the subscosta and the costa, with the presence of a spine more long than the spinules which border the costa. See photograph below.
 

Wing anterior edge venation of the unidentified look-alike species.
 

The venation of the wing anterior edge of the look-alike species is that of the Muscidae family, but also that of several other Diptera families. And in these families, I have found several dozens of completely black flies.

So I was not able to determine the taxonomic designation of the look-alike species.

I also observed that the look-alike fly shows differences with Silba adipata McAlpine in terms of pillosity : more bristles on the top of the head ; presence of numerous bristles on the top of the prescutum and the scutum ; significantly longer hairiness on the abdomen ; bristles on the lower face (below the antennae), forward and on the underside.

Below, a photograh showing the Black Fig Fly look-alike species.

We note the details of the wing anterior edge and the clear difference of pillosity with the Black Fig Fly.
 

Unidentified look-alike species.
 

I also have noticed that the legs of the unidentified look-alike species seem longer than those of Silba adipata McAlpine. See photograh below.

We note that the millimetric graduations indicate a body length of 5 mm.
 

Unidentified look-alike species.

 

Retour début article Summary

 

DETECTING THE BLACK FIG FLY

 

THE BLACK FIG FLY FLIGHT : A MAJOR DETECTION MEAN - videos

The Black Fig Fly walks slowly, but its flight is very fast.

And it has a characteristic which enables to easily identify the Black Fig Fly (with some practice…) : it is a sharp zigzag flight, composed of permanent back and forth 30-50 cm (12- 20 inches) in length, in all directions.

When very close to the targeted leaf, twig, or ripe fig, the Black Fig Fly moves back and forth much shorter (about 5 cm – 2 inches), and progressively slower, before ending up landing.

Inside the fig tree, the Black Fig Fly moves from one place to another by shorts direct flights, but keeping its specific lively zigzag way of flying, even for a very small distance.

This way of flying is also a major detection mean, because (especially if several flies are involved) it induces a lot of movements at the fig tree periphery that we cannot miss.

Taking in account the importance of being able to recognize the Black Fig Fly flight, I have published a specific page, which only contains two videos : flights at a fig tree periphery (27 s) ; approach flight and landing on the underside of a fig tree leaf (10 s)

I automatically launch the videos loading as soon as the page is called, but please wait for the loading of the half of the video before playing it (full screen mode recommended).

See page.

Note : it is not uncommon to find zigzagging insects around the fig tree, or flying through the fig tree. Special attention should be paid to two points to avoid confusion with the Black Fig Fly's flight pattern : generally, these insects have a much slower zigzagging flight ; and, they fly more or less horizontally, not coupling to their zigzags a sharp repetitive vertical displacement (as the Black Fig Fly does).

Below, photograph 1 : a Silba adipata McAlpine female flying towards an unripe fig for eggs-laying.
 

Black Fig Fly (Silba adipata McAlpine) : flight.
 

Below, photograph 2 : a black fig fly joining two others to feed on a cut fig tree leaf petiole.
 

Black Fig Fly (Silba adipata McAlpine) : flight.

 

WHERE TO FIND THE BLACK FIG FLY ON A FIG TREE ?

It is difficultt to see the Black Fig Fly on a fig tree.

The fisrt reason is its tiny size (most often 4 mm long).

The second reason is that, during its stay on the fig tree, it remains almost all of its time on the underside of the leaves, on which it directly lands, and where it feeds and performs its perpetual grooming activities, walking slowly or keeping motionless during long whiles. It rarely lands or walks on the upperside of the leaves, that it does not appreciate, Most often, a black fly on the upperside of a leaf is not the Black Fig Fly, but one of its lookalikes.

The Black Fig Fly is never on the trunk or on the gray wood (branches, twigs one year old and more), which do not attract it. It lands and walks only on the twigs of the year, which are green, then turn brown during the season.

Regarding the figs, the Black Fig Fly is not interested in the unripe green figs for feeding and it is rarely found on one of them. But it is greedy for ripe and overripe figs, on which it most often directly lands.

The case of a Black Fig Fly female which arrives on the fig tree in the situation of eggs-laying need is quite particular : from its arrival until its departure after having performed its sequence of successive eggs-layings (up to 20 visited unripe figs), it touches only green unripe figs and cannot be seen on any other part of the fig tree.

To increase the chances for seeing the Black Fig Fly, it is advisable to especially examine the shaded or semi-shaded parts of the fig tree, because it does not like the sun (even if it is protected from it by the leaf under which it remains). And to look under the leaves of the periphery, because the Black Fig Fly does not directly lands under those of the inside.
 

Black Fig Fly (Silba adipata McAlpine) on the underside of a fig tree leaf.

 

Black Fig Fly (Silba adipata McAlpine) on the underside of a fig tree leaf.

 

ACTIVITY PERIODS OF THE BLACK FIG FLY DURING THE DAY

Regarding the black Fig Fly activity periods during the day, I have observed two very different behaviors, depending on the type of activity : eggs-laying or feeding.

Eggs-laying activity.

For one given fig tree, during the intense Black Fig Fly attacks phase in the season (concentrating 75 to 97 % of the attacks during 12 to 23 days), I observe that the eggs-layings have no particular occurrence periods during the day. They are randomly distributed in all the time slots of the day.

But I have noted that for one considered fig tree, the eggs-laying activity is discontinuous during the day (up to several hours without any eggs-laying females on the tree), altough it is regular thoughout the week (eggs-laying females can be observed each of the days on the considered fig tree).

Feeding activity.

Feeding constitutes the main part of the Black Fig Fly activity on the fig tree, and I observe a strong activity for two periods in the day.

The first is the early morning. The feeding activity begins when the sun rises. More precisely, when it is not yet directly striking on the foliage, but the day is already clear. Then the feeding activity continues until the sun strongly strikes on the whole fig tree.

The second is the end of the afternoon and twilight, and even more when nightfall is approaching

It may happens that I observe a very reduced activity later in the morning or earlier in the afternoon, but it is very rare.

Observation of usual attendance times and usual attendance fig tree areas.

Within the two feeding activity periods, I have remarked the existence of usual attendance times : for one given fig tree, the feeding black fig flies are present in the same time slots from one day to the next. This whatever the month in the season, and for fig trees of various varieties. For example, in June 2016, they daily arrived from 4 pm to 4.30 pm on my ‘Bellone’ fig tree, and in September of the same year, they daily appeared from 6 pm to 6.30 pm on my ‘Col de Dame Noire’ fig tree.

I add that, for one considered fig tree, as it exists usual attendance times, it exists usual attendance areas : during the day, the black fig flies frequent a preferred area on the fig tree, the same from one day to the next (and the same from one year to the next…).

So, if you detect feeding black fig flies on a fig tree, note the time and the concerned area on the tree. The following days, come and observe the black fig flies at the same time and in the same fig tree area.

Of course, this a general phenomenon, which may suffer from some exceptions. Moreover, I think that everyone should check in his own orchard the existence of usual attendance times and usual attendance fig tree areas. For these, I made observations only in my orchard.

Below, the first photograph illustrates the eggs-laying activity, and the second illustrates the feeding activity.
 

Black Fig Fly (Silba adipata McAlpine) ; eggs-laying under an ostiolar scale of an unripe fig.

 

Black Fig Fly (Silba adipata McAlpine) feeding fig tree latex.

 

HOW TO DETECT THE BLACK FIG FLY ON A FIG TREE ?

The Back Fig Fly is difficult to see on a fig tree. For detecting it, we have a mean based on its incredible avidity for the fig tree latex (which is not the sap).

Choose a peripheral leaf (as big as possible) in the shaded or partially shaded part of the fig tree, at a height of 1 to 1.50 m (to well see the result), and tear the leaf from the twig. You will observe on the twig a large latex influx at the place where the petiole was attached. There is also latex oozing at the end of the torn petiole. Spread this latex along the twig below the latex influx, using the petiole as a paintbruh. Then stays at 2 m from the fig tree to observe the result.

If there are black fig flies on the fig tree, the first of them will land beside the latex influx after 30 seconds to a few minutes. If after a quarter of an hour, you have seen no flies, be sure that there are currently no black fig flies on the fig tree. But they may arrive one or two hours after, and they will be immediately attracted by the latex influx place, even if the latex has partially dried. The latex will remain attractive for the black fig flies the next two days, but less and less along the time. Note that there is no another fly or insect wich could be attracted by the latex influx.

Once a black fig fly is absorbed in its latex sucking task, if you avoid sudden movements, you can approach the camera up to 2 cm ( 0.8‘’) from the fly. There is usually from 1 to 3 black fig flies on the fig tree, at certain periods 4 to 5, very rarely 6 or 7. And if you use a hand-held sprayer filled with an insecticide allowed by the phytosanitary regulations, you will have the pleasure to instantly eliminate a group of black fig flies sucking the latex.

I observe in my orchard that the black fig flies frequent more intensely the fig tree for feeding activities in early morning and in very late evening. Using the detection mean at these periods of the day increases the chances to see black fig flies, but it can often be used successfully regardless of the time of day. And using it every two hours from dawn to night permits to know the distribution during the day of the black fig flies presence.
 

Black Fig Fly (Silba adipata McAlpine) feeding fig tree latex.

 

Black Fig Fly (Silba adipata McAlpine) feeding fig tree latex.
 

A very efficient variant.

Instead of tearing the leaf from the twig, cut its petiole at about a 3 cm (1.20") length. Spread along the cut petiole the latex oozing at the end of the detached part of the petiole.
 

Black Fig Fly (Silba adipata McAlpine) feeding fig tree latex.

 

Black Fig Fly (Silba adipata McAlpine) feeding fig tree latex.

 

DETECTING THE BLACK FIG FLY ON A FIG TREE WHEN THE LEAVES ARE NOT YET DEVELOPED

Debarking a fig tree branch one year or older (grey wood of all sizes) is a method of detecting the presence of Silba adipata McAlpine.

It is particularly useful at the very beginning of spring, when the foliage is poorly developed, thus the leaves cannot be torn, or their petiole cut, to cause a latex influx.

Debarking causes latex exudation which, although faint and not visible, gives off a distinctly smelling odor and attracts Silba adipata McAlpine if it is on the fig tree.

Careful observation of Silba adipata McAlpine on a debarked fig tree branch reveals a particular behavior : it spends a large part of its time sucking the narrow greenish strip separating the bark from the sapwood, and visible all along the perimeter of the debarked area.

This is the bast zone, in which the concentric rings of laticiferous vessels (containing the latex) are located, in addition to the sieve tubes conveying the sap which results from photosynthesis carried out in the leaves.

This Silba adipata McAlpine behavior is the same as that observed when it is attracted to a pruning wound of a fig tree branch.

Below,

Photograph 1 : a black fig fly attracted to a debarked fig tree branch.

Photograph 2 : a black fig fly sucking the bast zone on a debarked fig tree branch.
 

Black Fig Fly attracted to a debarked fig tree branch.

 

Black Fig Fly sucking the bast zone on a debarked fig tree branch.

 

DETECTING THE BLACK FIG FLY ON A FIG TREE USING AN INFESTED FIG

While breaking unripe attacked figs during my larvae searches, I noticed that their inside is sticky and that after the operation a strong latex smell remains on the fingers.

I then had the idea of laying bare the inside of infested unripe figs without detaching them from the branch, by making a double cut with the secateurs (one vertical and one horizontal).

I have observed that this method is attractive for the Black Fig Fly, but less than tearing a fig tree leaf (which provides a much larger and more concentrated quantity of latex).

Below, two photographs of a black fig fly attracted to a reddened small unripe infested fig left on the tree with the inside laid bare.
 

A black fig fly attracted to a small reddened unripe infested fig with the inside laid bare.

 

A black fig fly attracted to a small reddened unripe infested fig with the inside laid bare.

 

BLACK FIG FLIES AERIAL GROUPS OBSERVATIONS
 

Aerial swarms.

Formation of aerial swarms is a rather common phenomenon among the Lonchaeidae family, to which Silba adipata McAlpine belongs.

Reference : McAlpine, J. F. & Munroe, D.D. 1968. Swarming of lonchaeid flies and other insects, with descriptions of four new species of Lonchaeidae (Diptera). Can. Entomol. 700: 1154-1178.

B. I. KATSOYANNOS, while studying Lamprolonchaea smaragdi Walker swarming in the Chios Island (Greece), in 1982, had the opportunity to observe a Silba adipata McAlpine swarm, but only once (on August 20, 1982).

Reference : KATSOYANNOS B. I., 1983, Swarming of Lamprolonchaea smaragdi Walker (Diptera, Lonchaeidae) and a few other Diptera observed in Chios, Greece, Bulletin de la Société Entomologique Suisse, vol. 56, pp. 183 -185.

The author describes this aerial swarm as follows.

« The swarm occurred in a free space of 2 m between two large branches of a fig tree and consisted of ca. 20 individuals flying very rapidly in a pattern similar to that observed for Lamprolonchea smaragdi. The swarm danced mostly in the shade and was difficult to notice, because of the very rapid flight pattern. Of 8 specimens netted, only one was a female. The flies in the swarm moved extremely rapidly in a whirling pattern. The axis of the movement approximated the horizontal plane. The overall shape of the swarms was rather elliptic, occupying a space of 1-2 m in diameter. Usually the swarms were more or less stationary. However, from time to time, they changed their location slightly, moving horizontally or vertically ».

I regularly perform observations of black fig flies groups flying in a similar way between two trees, but I do not qualify these as aerial swarms because the groups only involve two to three specimens.

The group performs repetitive flights, more or less on the horizontal plane and limited to an elliptic space, with an amplitude of about 2 m (6.5 ft), at a height of about 1.5 m (5 ft). The aerial group is rather stationary, but Inside the group the flies permanently keep their very fast zigzaging characteristic flight pattern (for this pattern, see page).

I can observe this phenomenon for long whiles, sometimes more than one hour, in the late afternoon, at dusk.

Over the season, I regularly perform this type of observations at two places : between my ‘Bellone’ variety fig tree and an oriental persimmon (in June), and betweem an olive tree and a silky oak, near a hedge, at 30 m (100 ft) from my fig trees (during certain periods of summer).

I think that these black fig flies grouped in the air are males waiting for females, or males and females just before mating (or mating).

 

Other aerial groups observations (2 to 3 specimens).

I can report two other observations about the Silba adipata McAlpine aerial groups.

The first is the common feeding activity at the periphery of the fig tree. Black fig flies have a gregarious behavior. So, when a flying individual brushes against another which is on a twig or on a leaf underside, most often the latter joins it in a swirling flying duo (thiscan be observed on the first video page).

The second is a one-off observation. In June 2019, I was on my observation post near my ‘Bellone’ fig tree, to check the effectiveness of glue micro-traps baited with fresh latex, and I was surprised by the arrival of a pair of black fig flies that I distinctly saw coming from the outside of the fig tree. With their caracteristic flight pattern, they dived at highspeed towards a glue micro-trap.

They seemed to touch the trap, but they sharply moved away at the last moment, without landing on it. Then, starting from a distance of about 1 m, they strictly repeated the same operation, and left the fig tree without separating. I deduced that the glue was repellent for them, and I was impressed by the perfect flights synchronisation of these two black fig flies.

Below, two photographs showing a Black Fig Fly flight during feeding activity.
 

Black Fig Fly (Silba adipata McAlpine) flight during feeding activity.

 

Black Fig Fly (Silba adipata McAlpine) flight during feeding activity.

 

CAN WE HEAR THE BLACK FIG FLY WHEN IT IS FLYING, AND THUS DETECT IT ?

The flight of the Black Fig Fly is perfectly silent, whatever the distance at which the insect is, and whatever the circumstances (approach flight towards the fig tree, moving from one point to another in the fig tree to feed or to lay eggs, sudden take-off following a movement that disturbs it...). And this, even if the black fig flies are two or three to fly together.

I can no longer count the number of times a black fig fly suddenly flew away when I had approached the camera to 0.40” (1 cm) from it, so when it was to 8“ (20 cm) from my ear, and I never heard it despite the surprising speed of its flight.

Over the years of observing the Black Fig Fly, I have had the opportunity to experiment close contacts with it, and all of which confirmed the absence of sound detection possibility of its flight.

For example, when black fig flies came and landed on my camera while I was photographying them, or more rarely when a black fig fly landed on my trousers at the observation post in the field, or at home when I practiced black fig flies breeding.

To be complete with the contacts that I had the opportunity to live with the Black Fig Fly, I take this post to report an extremely rare direct physical contact.

In September 2016, I was photographying a black fig fly feeding on a ripe fig of the 'Col de Dame Noire' variety, when I saw in lateral vision at 20” (50 cm) from me the characteristic flight of an individual of the species.

I stepped back slowly, hoping to be able to photograph it together with the other. Holding my camera only in my right hand, I was surprised to see that the black fig fly landed, not on the ripe fig as I hoped, but on the top of my left hand, which was horizontally at 8” (20 cm) from the camera.

It began to walk slowly over the top of my hand, licking it with its unfolded oral tube. When it approached the edge of the hand, I turned the latter very slowly so that the fly passed over the palm while continuing to walk. The black fig fly even climbed along my fingers, and it stayed thirty to forty seconds on my hand, before vigorously but silently flying away.

I think that the black fig fly was attracted by the presence of latex traces on my hand. A few moments before, I had handled the petioles of fig tree leaves torn off to cause latex oozes.

Note : the Black Fig Fly's flight cannot be detected by sound since it is completely silent. But this character constitutes a discriminating factor : any look-alike fly which would be detectable by sound during its flight can be considered without a doubt as not being the species Silba adipata McAlpine.

Below, two photographs of my exceptional encounter with the Black Fig Fly.
 

 


 

During my photography sessions of black fig flies at home (flies from my breeding), I saw only once one of them land on me.

Among other exercises, I photographed them in close-up on my kitchen window glass.

I used to gently drop down with a long and very thin wand those that had climbed too high while walking, so that they landed lower on the glass after quickly freeing themselves from the wand tip by a short vertical agitated flight (when they did not fly off to stick to the ceiling ...).

One of the flies dislodged from the window glass landed on my leg, as I sat down to rest while continuing to photograph.

I did not move my leg and it stayed for about thirty seconds before spontaneously leaving it, perhaps not finding to her liking the canvas of the jeans I was wearing ...

During all of these close contacts with the black fig flies, I never heard them despite the general agitation of the flies population participating (by force more than willingly ...) in the various "proposed" exercises.

In the field, during my many hours of observation and photography, I only experienced the same situation on two occasions : a black fig fly landed on the top of my leg, while I was sitting at the observtion post.

In both cases, the fly did not stay very long and I was not able to benefit from a good light incidence to achieve fairly sharp photographs.

During these observations, I noted that the black fig flies took off very quickly, but quite silently.

Below, two photographs (at home) showing a black fig fly companion on my jeans.
 

A black fig fly on the observer's jeans.

 

A black fig fly on the observer's jeans.

 

Retour début article Summary

 

ATTACKS CHARACTERISTICS

 

I think that it is important to know for the Black Fig Fly the characteristics of the eggs-laying, the behaviour of the female, and the attacks variability over the season and from one year to another. This allows to optimize the implementation of the existing control methods and to imagine new ones.

Below, my personal observations (no information reported from the literature).

 

EGGS-LAYING CHARACTERISTICS

1. The Black Fig Fly lays eggs only in green hard unripe figs. It does not attack ripe figs.

I nevertheless regularly find larvae (alive or dead), pupae, and even desiccated remains of young imagos, in ripe figs.

Using my method (which will be progressively improved) for determinig the date of the fig attack with the date of the exit holes appearance or with the size of the larvae, I have always verifed (for my own cases and for those that were submitted to me) that the attack occurred at the unripe stage of the fig. I do not rule out, of course, the possibility that one day a photograph will prove to me the existence of exceptions.

I have observed that the attacked figs which reach the maturity stage (and usually the overripe stage, then the desiccation phase on the tree) represent 2 to 5 % of the global production of the fig tree, depending on the year and the fig variety.

2. The Black Fig Fly lays its eggs under the ostiolar scales (never through the fig skin).

Its ovipositor is to weak to pierce unripe figs. Generally, the eggs are laid under an horizontal scale of first level (i. e. the ones that are on the surface of the fig), and for a small part, under a second level scale. In rare cases, when the ostiole has slightly widened, I find eggs in the ostiolar canal, more or less vertically laid (for 2 videos of the eggs-laying, see page).

3. The female lays from 1 to 4 eggs in each visited fig, often 3.

If there are several eggs, these are generally grouped under the same ostiolar scale.

4. The smallest size that I observed for an attacked fig is a diameter of 1.1 cm (0.43").

The attacked figs with a diameter of 1.3 to 1.5 cm (0.50 to 0.60") are not rare. I give the diameter of the fig at the date of the eggs-laying, not the one when it is possible to detect that the fig is infested. In fact, the diameter of all the attacked figs continue to increase after the eggs-laying, although the activity of the larvae (0.5 to 2 cm - 0.20 to 0.80" - depending on the period in the year of the eggs-laying, the fig variety and, for a given variety, the figs individualy considered in the same crop).

5. When a fig has reached a certain size at the unripe stage, the Black Fig Fly does not attack it. The fig can be considered as saved .

It exists exceptions, but they are not numerous for a given crop. The "save size" depends on the variety, and on the crop for the biferous varieties. For instance, it is 2.8 cm (1.10") - diameter - for the uniferous varieties 'Bellone' and 'Col de Dame Noire', and it is 3.8 cm (1.5") for the breba crop of the 'Grise de la Saint-Jean' variety.
 

Below, two photographs related to the eggs-laying.

Photograph 1 : a Black Fig Fly female laying eggs under an ostiolar scale of an unripe fig.

Photograph 2 : three Black Fig Fly eggs under an ostiolar scale of an unripe fig.
 

 

 

FEMALE BEHAVIOR

1. The female performs an uninterrupted sequence of successive eggs-layings on the same fig tree.

When the female Black Fig Fly arrives on a fig tree in situation of eggs-laying need, it directly lands on a fig and lays eggs under its ostiolar scales. Then it immediatly performs an uninterrupted sequence of successive eggs-laying which can involve up to 20 figs.

The sequence may be short (generally 3 to 5 visited figs), medium (generally 9 to 13 visited figs), or long (15 to 20 visited figs). The sequence duration is variable : generally from 20 mm to 1 h 30, with exceptions that are shorter or longer. It depends on the number of visited figs and on the average time spent on each fig by the female. This time may be surprisingly different from one female to another. And it usually varies for the same female from one visited fig to another.

2. During the sequence, the female often lays eggs in figs in which other females have previously laid eggs. And it happens that it lays eggs twice in the same fig during a same sequence. I observed up to 29 empty eggs envelopes (chorions) under the ostiolar scales of one unripe fig. We even have published a video showing two females which are simultaneously laying eggs in the ostiole of the same fig (see page).

3. During the sequence, the female is completly absorbed in its eggs-laying task.

It never rests and it is not interested in any food source, even by fresh latex oozing near the fig, of which it is usually very avid. It is not disturbed either by the other black fig flies which may come on the fig near it, or brush against it while flying, what usually would have made it fly off the tree in a swirling duo.

From these observations of the female Black Fig Fly behaviour, I draw the conclusion that a trap baited with a food-attractant (whatever it is) never captures a female of this species which arrives on the fig tree in situation of eggs-laying need, therefore never prevents it from carrying out its harmful activity on the crop. The action of such a trap is only at the level of the overall pressure of the black fig flies population in the region, as it captures a part of the females and the males which are feeding on the fig tree (prophylactic role).

4. At the end of the sequence, the female leaves the fig-tree.

It does not remain on it to feed.

So,  I am inclined to consider that a Black Fig Fly female which has performed its eggs-layings sequence has only touched unripe figs during its visit on the fig tree.
 

Below, a photograph showing a Black Fig Fly female laying eggs under an ostiolar scale of an unripe fig.
 

Black Fig Fly female laying eggs under an ostiolar scale of an unripe fig.

 

TWO MUTUALLY EXCLUSIVE ACTIVITIES DURING A STAY ON A FIG TREE

I never observed that a female feeding on the fig tree (underside of the leaves, twigs of the year, ripe figs, latex oozing...) suddendly gives up its activity to start laying eggs.

As previously indicated, I observed that an eggs laying female never interrupts for feeding activities its sequence of successive eggs-layings on a fig tree (up to twenty visited figs...), and that it always leaves the fig tree at the end of the sequence.

Taking into account these observations, for a Black Fig Fly female, eggs-laying and feeding are two mutually exclusive activities during a stay on a fig tree.

And I consider that the black fig flies population on a fig tree at a given time is composed of two strictly distinct categories : the "feeding flies" (females not in a situation of eggs-laying need, and males) and the "eggs-laying flies" (female performing their eggs-layings sequence), and that a black fig fly does not change category during its stay on the fig tree.

In addition, the feeding activity is permanent throughout the season, while, according to my observations, the eggs laying activity is concentrated over a short period of the season, variable depending on the variety and the location of the fig tree (and starting as soon as the unripe figs reach the critical diameter for being attacked by the Black Fig Fly).

After the intense attacks phase, the attacks are weak, then zero until the end of the season, even though the fig tree still bears many unripe figs of all sizes.

In a rigorous approach, I invite you to check if my observations and my overall interpretation are transposable in the specific environment of your own orchard.

 

STERILE EGGS-LAYING - FALSE EGGS-LAYING - FIGS TESTS

If a fig has reached maturity without being infested although you have observed a Silba adipataMcAlpine female on its ostiole with an eggs-laying behavior, there may be two explanations : sterile eggs-laying or false eggs-laying.

Sterile eggs-laying.

A sterile eggs-laying is a deposit of unfertilized eggs, made by females that have not mated (therefore the spermathecae of which are empty).

B. I. KATSOYANNOS studied in 1981 and 1982 large populations of black fig flies in the island of Chios (Greece).

Reference : KATSOYANNOS B. I., 1983, Field observations on the biology and behavior of the black fig fly Silba adipata McAlpine (Diptera, Lonchaeidae), and trapping experiments, Z. ang. Entomol. 95, pp. 471-476.

The author reports that he did not observe matings in the breeding boxes with the flies he obtained from larvae contained in figs infested with Silba adipata McAlpine. He indicates that more than 2,000 eggs were deposited by the females in the unripe figs made available to them, but that none of these gave birth to a larva.

What he interprets as the consequence of an absence of matings.

I do not know the sterile eggs-layings rate that exists for Silba adipataMcAlpine in nature. I have no personal observations and I have not found anything in the literature.

False eggs-laying.

A false eggs-laying is the name I have given to the phenomenon according to which, during the sequence of successive eggs-layings of a female on the same fig tree, some of the figs on the ostiole of which the female has had an eggs-laying behavior for a significant time are not infested.

No detection of eggs, nor of empty eggs envelopes (chorions), under the ostiolar scales or in the ostiolar canal, during the examination with the stereomicroscope.

I personally observed this phenomenon on four figs (two figs each time during two eggs-layings sequences separated by several months on two different fig trees).

I discovered the phenomenon during eggs-layings timing sessions followed by the examination under stereomicroscope of the figs concerned by the eggs-layings. The duration of eggs-laying behavior of the female on each of the four figs was 1.5 to 2 minutes.

I was able to observe that the other eggs-layings belonging to the same sequence as that of the false eggs-layings gave rise to a fig infestation.

The number of observations is too low to be able to determine a percentage of occurrence for the false eggs-layings, and I do not know the cause of the latter.

Figs tests behavior.

The phenomenon of false eggs-layings should not be confused with the figs tests behavior.

According to my observations of the eggs-layings sequences, between two figs in which it successively lays eggs, the Silba adipata McAlpine female briefly visits one or more figs without laying eggs in them, seeming to test these figs.

This behavior is almost systematic (only very short eggs-layings sequences can be devoid of it), and the number of tested figs between two successive eggs-layings varies from 1 to 5.

I do not know the reason for the figs tests between two successive eggs-layings.

It should be noted that this cannot be a question of ruling out figs that are already parasitized. Indeed, direct observations of eggs-layings sequences and examination of the sizes of the larvae contained in a same fig show the existence of the plurality of eggs-layings in the same fig (for about 20% of the attacked figs).

According to my observations, multiple eggs-layings in a same fig can occur during the same eggs-laying sequence, in two sequences of the same day, or on the occasion of sequences spaced several days apart.

 

Retour début article Summary

 

ATTACKS  OBSERVATIONS OVER THE SEASON

 

VARIABILITY OF THE ATTACKS OVER THE SEASON
 

1. I observe a variability of the attacks of the Black Fig Fly over the season, responding to a general model.

The attacks model shows the existence of 3 phases :

- A phase 1 of intense attacks concentrated on a short duration. For a given fig tree, this phase concentrates 75 % to 97 % of the eggs-layings of the season, and lasts from 2 to 3 weeks, depending on the variety and the tree location. Knowing that its intensity (eggs-layings percentage) is not proportional to its duration.

- A phase 2 of very low level attacks, during which the number of attacks is always significantly lower than the number of unripe figs of the size required for the attack that are present on the tree.

- A phase 3 of total absence of attacks despite the presence on the tree of unripe figs of the size required for the attack.
 

Note 1 : the level of attacks (therefore the percentage of crop loss) is totally independent of the variability of these over the season.

The severity of the season attacks depends on the percentage of affected figs - related to the global crop - during the phase 1.

And the percentage of crop loss for the season is also totally independent of the percentage of eggs-layings during the intense attacks phase.

From one fig tree to another, 97 % of the attacks during the intense attacks phase can affect only 20 % of the crop, as 75 % of the attacks during the same phase can affect 75 % of the crop (resulting in a final crop loss of 100 %).

I observed that the level of the attacks in an orchard is the conjunction of three factors : the orchard location in the region affected by the Black Fig Fly (by far the most decisive factor), the figs varieties susceptibility to the Black Fig Fly, and the specific Black Fig Fly activity level for the considered year. 

Note 2 : during the phases 2 and 3, I observe the permanent presence on each of the fig trees of 1 to 3 feeding Black Fig Fly females.

 

2. The general model of the attacks of the Black Fig Fly is declined with some differences from a fig tree to another.

The differences exist for the 3 phases, and depend on the fig variety and, for the biferous varieties, on the nature of the crop (breba or second crop).

They relate to the duration and the intensity level for the phase 1, and to the duration for the phases 2 and 3.

Some examples, for the year 2019, in my orchard.

For the phase 1 : 'Bellone' variety 90 % of the attacks / 12 days ; 'Col de Dame Noire' 97% of the attacks / 23 days ; 'Grise de la Saint-Jean', breba crop 75 % of the attacks / 17 days, 'Grise de la Saint-Jean', second crop 88 % of the attacks / 20 days.

For the phase 2 : duration 3 to 5 weeks for 'Bellone', 'Col de Dame Noire' and 'Grise de la Saint-Jean' (second crop), 2.5 months for 'Grise de la Saint-Jean' (breba crop).

For the phase 3 : duration of 3 to 6 wweks for 'Bellone', 'Col de Dame Noire' and 'Grise de la Saint-Jean' (second crop), 8 days for 'Grise de la Saint-Jean' (breba crop).
 

Important : for the variability of the attacks over the season, I am sure of my observations in my orchard, but I am not sure that they are unviversal in scope. I suggest to check in other regions if there is a variability of the attacks over the season, and if yes, if it is more or less in accordance with the exposed attacks model. This remark particularly applies to commercial orchards, for which I have no observation in my region for a possible variability of the attacks.

 

3. For a given fig tree, the start date of the intense attacks phase varies from year to year (sometimes a 2 weeks variation).

We must keep in mind that, the criterion that triggers this phase is not a date, but the attainment of the critical diameter for the Black Fig Fly attack (0.40’’ - 1 cm) by the unripe figs, on the considered fig tree.

In practice, I consider that this is the case when the five largest figs on the tree have reached this diameter (measurement with a vernier caliper ; measuring the largest diameter of the fig, the syconium not being a regular sphere).

 

4. During the phase 1 (major part, or almost the totality, of the attacks of the season concentrated during a short duration), the population of the fig tree does not increase.

During this period, there are permanently more feeding females on the fig tree than there are eggs-laying females.

Knowing that the number of black fig flies that frequent a fig tree is low. I regularly observe only from 1 to 3 black fig flies on one fig tree (whatever its variety - dimensions of the considered fig trees : 4 m high and 4 m wide).). At certain periods in the season, and depending on the hour in the day, this number can reach 4 or 5. I exceptionaly observed 6 black fig flies on the same fig tree, and once only 7.

 

5. The paradoxical observation of a non-increase of the fig tree population during the period of intense attacks is explained by the way in which the Black Fig Fly females come to lay their eggs on the fig tree.

In fact, during this period, there is generally only one eggs-laying female at a time on one fig tree. And, altough the eggs-laying activity is regular (eggs-laying females can be observed each of the days for one considered fig tree), it is discontinuous during the day (up to several hours in the day without any eggs-laying females on this fig tree).

Certains days, I observe two eggs-laying females at a time on one fig tree, and exceptionaly (once only), I observed 4 females laying their eggs at the same time on one fig tree.
 

Note : the observation of the eggs-laying females flow on a fig tree is only possible under demanding conditions : fig tree severely (but selectively) defoliated, continuous presence during several hours on the observation post each of the days of the intense attacks period, and, in addition to careful observation from the post, slow walk aroud the fig tree every quarter of an hour with a meticulous inspection of the figs groups.
 

Below, a photograph showing a Black Fig Fly female laying eggs under an ostiolar scale of an unripe fig.
 

Black Fig Fly female laying eggs under an ostiolar scale of an unripe fig.

 

VARIABILITY OF THE ATTACKS FROM ONE YEAR TO ANOTHER

My orchard is located in a place that is very susceptible to the Black Fig Fly, but which has not known in recent years significant variations in winter temperatures (usually mild), nor late frosts (non-existent in my region).

I therefore do not have personal observations on the lethal temperature for the Black Fig Fly.

None of my correspondents gave me indications on this subject, and so far I have not read in the French or foreign specialized literature the mention of a precise, or even approximate, lethal temperature.

In France, the Black Fig Fly is confined in the extreme south of the country, in the Mediterranean region, from the Spanish border to that of Italy.

It is particularly active in a coastal strip 18 miles (30 km) wide, but according to the observations reported by some of my correspondents, it is found in plains with a mild climate up to 90 miles (150 km) from the sea (Toulouse - Avignon line).

According to the observations of the permanent contributors to the present website who technically advise professional figs growers (and therefore closely monitor the annual activity of the pest in commercial orchards), we find for the Black Fig Fly the two population variations trends observed for the other fruit flies in relation with the winter climate. Especially the medfly and the olive fly, with which the population variations from one year to the next are synchronized.

If the winter is mild and wet, the conditions are favorable for the appearance in the spring of large populations of black fig flies.

If the winter is cold, with the presence of significant frosts, the populations appearing in the spring are reduced.

In addition to these two general trends, it has been noted that the occurrence of severe late frosts considerably limits the black fig flies populations.

A significant example is the exceptional climatic accident that occurred in the southwest of France, which Margaux ALLIX and Bernard PEYRE reported to me.

On April 20, 2021, an exceptional cold wave hit this region causing temperatures to drop from 26,6 to 21,2 °F (-3 to -6 °C) in commercial fig orchards, depending on the spots. And the cold (of varying intensity) continued for two or three days.

In certain orchards, all the shoots of the year froze and restarted, causing a fruiting delay of two to three weeks.

Following this climatic accident, Margaux ALLIX observed that in fig trees orchards usually moderately susceptible to the Black Fig Fly, damages due to the pest were almost zero, and in susceptible ones, they were low (< 5 %).

But she noted that, in an orchard usually very susceptible to the Black Fig Fly, damages were more important (for example, 1 to 2 figs per branch for the ‘Panachée’ and the ‘Longue d’Août’ varieties).

Below, two photographs illustrating the Black Fig Fly eggs-laying activity.
 

A Black Fig Fly female laying eggs under an ostiolar scale of an unripe fig.

 

A Black Fig Fly female laying eggs under an ostiolar scale of an unripe fig.

 

LAST EGGS-LAYINGS AND PRESENCE IN THE SEASON

F. SILVESTRI observed in the region of Portici, near Napoli, that the last eggs are deposited in November in the mamme of caprifig trees. He also indicates that fresh eggs can be found in figs of the domestic fig trees until October.

Reference : SILVESTRI F., 1917, Sulla Lonchaea aristella Beck. (Diptera : Lonchaeidae) dannosa alle infiorescenze e fruttescenze del caprifico e del fico, Bollettino del Laboratorio di Zoologia Agraria in Portici, vol.12, pp. 123 -146.

R. PUSSARD gives interesting personal information : in 1949, in Cap d'Antibes (France), he observed on October 9 a female laying eggs in a fig of the 'Bellone' variety the size of a hazelnut ; the same year, the catches of Silba adipata McAlpine adults were still very numerous from November 20 to 25, and they did not cease until December 21.

Reference : PUSSARD R., 1950, A propos de la mouche noire des figues Lonchaea aristella Beck., comptes rendus des séances de l'Académie d'agriculture de France, T. 36, pp. 144-145.

Marc SCHAISON, a fig trees collector in Draguignan (Var French department), reported to me that the latest Silba adipata McAlpine eggs laying that he observed on his trees occurred on October 12, 2014, in mid-day, in an unripe fig of the 'Brown Turkey' variety.

Alain COSTA., who is one of the permanent contributors to the present website, reported to me that in the Albatera region (near Alicante, in Spain) the figs of the ‘Blanca’ late variety are still attacked by the Black Fig Fly, and he sent me two photographs of these figs taken on December 13, 2019 (see below).

My own observations.

The latest eggs laying that I observed in my orchard took place on September 18, 2016, at 6:15 p.m., on a shrub of the 'Col de Dame Noire' uniferous variety (which is my latest fig variety). It was carried out in an unripe green fig 2.3 cm in diameter, while only two unripe figs and four ripe figs remained on the tree.

In 2017, I decided to leave my traps on the fig trees until December 31 to determine the end date of the Silba adipata McAlpine presence in my orchard.

The last Silba adipata McAlpine individual was captured on November 20.

I noted that the last ripe fig harvest in the orchard was performed on October 7 (i.e. 44 days before), while there were no more unripe figs, and that the last fig tree leaf of the orchard fell on November 15 (i.e. 5 days before).

This observation shows that Silba adipata McAlpine frequents a place where there are no longer any unripe figs in which to lay eggs, nor any ripe figs or fig leaves on which to feed.

Being pointed out that the Silba adipata McAlpine adults also feed on plants other than the Fig tree (without laying eggs - the Silba adipata McAlpine larvae feed and develop only inside figs).

Below, two photographs of unripe ‘Blanca’ figs that were still on the tree on December 13, 2019 (credit : Alain COSTA).

Photograph 1 : the unripe figs have a healthy appearance (except for one or more larvae exit holes on some of them).

Photograph 2 : the interior of the unripe figs shows traces of Black Fig Fly attacks.
 

Unripe 'Blanca' figs attacked by the Black Fi g Fly (December 13, 2019).

 

Unripe 'Blanca' figs attacked by the Black Fig Fly (December 13, 2019).

 

Retour début article Summary

 

EGGS LAYING ACTIVITY

 

FOUR DISTANT PHOTOGRAPHS OF EGGS LAYING ACTIVITY

To familiarize us with the presence of Black Fig Fly eggs laying females when we are walking around our fig trees : four distant photographs.
  

Black Fig Fly (Silba adipata McAlpine) female laying eggs under an ostiolar scale of an unripe fig.

 

Black Fig Fly (Silba adipata McAlpine) female laying eggs under an ostiolar scale of an unripe fig.

 

Black Fig Fly (Silba adipata McAlpine) female laying eggs under an ostiolar scale of an unripe fig.

 

Black Fig Fly (Silba adipata McAlpine) female laying eggs under an ostiolar scale of an unripe fig.

 

EGGS LAYING FEMALES SEEN FROM ABOVE

To familiarize us with the Black Fig Fly, two photographs of eggs laying females seen from above.
 

Black Fig Fly (Silba adipata McAlpine) female laying eggs under an ostiolar scale of an unripe fig.

 

Black Fig Fly (Silba adipata McAlpine) female laying eggs under an ostiolar scale of an unripe fig.

 

THE RODNEY ROCKAT'S VIDEO

In 2017, Bernard PEYRE, who is one of the permanent contributors to the present website, brought to my attention a YouTube video showing a Silba adipata McAlpine female laying eggs in the ostiole of an unripe fig, published on January 15, 2015 by Rodney ROCKAT.

The latter did not know the Black Fig Fly and believed to be dealing with the blastophagus. He therefore gave to his video the erroneous title "Awesome fig wasp in action". Thus, this video of great interest escapes searches for videos launched with the species Latin names (old and current), or with the common names in English or in other languages.

Given the high pedagogical interest of the information provided by the video, I saved it in the page of the present website dedicated to eggs-laying in order to prevent its loss in the event of a possible removal from YouTube. You will also find on this page one of my videos showing the Black Fig Fly eggs-laying, knowing that the two videos are accompanied by a detailed analysis (in French) of the female’s operating mode (performed via a freeze frame every two seconds...).

The country of origin of the video remains a mystery. It is not specified on YouTube, and Rodney ROCKAT did not answer the question on this subject asked in 2017 via the YouTube comments by Vladimiro ROCCO, an Italian member of our team.

 

Retour début article Summary

 

FEEDING ACTIVITY

 

OBSERVATION DURING THE RIPE FIGS PERIOD

When the fig tree bears ripe figs, the Black Fig Fly is less often on the underside of the leaves. It is greedy for ripe and overripe figs, on which it most often directly lands (it is not interested in the unripe green figs for feeding, and it is rarely found on one of them).

It also lands on the twigs of the year, and walking along them, it joins the ripe figs. It moves from one ripe fig to another in short direct flights (keeping its characteristic sharp zigzag flight).

This constitutes a new activity in the season by which we can detect the presence of the Black Fig Fly, knowing that the priority is to check the ripe figs. According to my observations, the black fig flies frequent the ripe figs located on the peripheral twigs, as they do for the leaves.

Below, two photographs which show the Black Fig Fly feeding on ripe figs ('Col de Dame Noire' variety).
 

Black Fig Fly (Silba adipata McAlpine) : feeding on ripe figs.

 

Black Fig Fly (Silba adipata McAlpine) : feeding on ripe figs.
 

When feeding, the Black Fig Fly doest not damage the ripe fig, since it only licks-sucks it.

Below, two photographs which show the Black Fig Fly feeding on the surface of a ripe fig ('Col de Dame Noire' variety).
 

Black Fig Fly (Silba adipata McAlpine) : feeding on ripe figs.

 

Black Fig Fly (Silba adipata McAlpine) : feeding on ripe figs.
 

The Black Fig Fly walks slowly on the surface of the ripe fig, lingering on tears or superficial long cracks in the skin, where it can suck the withish parenchyma (placenta), softened by the maturity.

Below, photograph 1 : a black fig fly is sucking the softened whitish parenchyma in a small skin tear on a ripe fig.
 

Black Fig Fly (Silba adipata McAlpine) : feeding on ripe figs.
 

Below, photograph 2 : a black fig fly is sucking the softened whitish parenchyma in a long superficial skin crack on a ripe fig.
 

Black Fig Fly (Silba adipata McAlpine) : feeding on ripe figs.
 

We can also find the Black Fig Fly on the infrutescence of more or less ripe figs which have burst on the tree (photograph 1), or on that of ripe figs which have been opened by the birds - magpies, in my orchard (photograph 2).
 

Black Fig Fly (Silba adipata McAlpine) : feeding on ripe figs.

 

Black Fig Fly (Silba adipata McAlpine) : feeding on ripe figs.

 

OBSERVATION OF TWO BLACK FIG FLIES ON A FIG TREE TWIG OF THE YEAR

Below, two photographs showing two black fig flies on a fig tree twig of the year, during feeding activity.
 

Black Fig Fly (Silba adipata Mcalpine) : two individuals on a fig tree twig of the year.

 

Black Fig Fly (Silba adipata Mcalpine) : two individuals on a fig tree twig of the year.

 

OBSERVATION DURING FEEDING ACTIVITY

Feeding activity at the top of a fig tree twig of the year : two females, recognizable by the abdomen end for one of them (sucking latex), and by the wide interocular space for the other (smoothing its front paws).
 

Black Fig Fly : feeding activity at the top of a fig tree twig of the year.

 

Black Fig Fly : feeding activity at the top of a fig tree twig of the year.
 

The black fig flies very often perfom in groups their feeding activities on the fig tree.

Below, photograph 1 : three black fig flies consuming fig tree latex.
 

Three black fig flies consuming fig tree latex.
 

Below, photograph 2 : two Black Fig Fly females on a fig tree twig of the year (the females are recognizable by their wide interocular space - that of the males being narrow).
 

Two black fig flies on a fig tree twig of the year.

 

LATEX ATTRACTIVENESS

The Black Fig Fly is attracted to the latex at the periphery of fig tree branches pruning wounds, whether on greenwish or brown year-old wood, or on grey old wood.

Below,

Photograph 1 : a black fig fly on a brown twig of the year pruning wound.

Photograph 2 : a black fig fly on a grey old wood pruning wound.

Note : careful observation of the two photograghs leads to highlighting a particular feeding behavior on the pruning wounds : the Black Fig Fly spends most of its time sucking on the greenish narrow circular area located just below the cork. This area contains the phloem sieve tubes (in which the sap resulting from photosynthesis in the leaves circulates in a bidirectional way), interspersed with concentric rings of latex vessels.
 

A black fig fly sucking latex at the periphery of a fig tree twig of the year pruning wound.

 

A black fig fly sucking latex at the periphery of a fig tree old wood pruning wound

 

FEEDING LATEX OOZINGS ON RIPE FIGS

The fig tree latex completely dries a few hours after it is exposed to air.

But, according to my regular observations, after being strongly attractive for the Black Fig Fly during several hours, it remains attractive (with, of course, a less intensity) during a two to three days period, altough dried.

I give an example : black fig flies are attracted to the latex drops that formed on the ripe figs surface through the medfly eggs-layings holes, and which have dried.

Below, two photographs showing a black fig fly which sucks a dried latex oozing, on the surface of a ripe fig.

We note that a circular purple spot has appeared near the eggs-laying hole of the medfly.
 

A black fig fly sucking a dried latex oozing on a ripe fig.

 

A black fig fly sucking a dried latex oozing on a ripe fig.
 

THe two photographs below illustrate latex oozing during a medfly eggs-laying in a ripe fig.

Latex oozings appearance on ripe figs surface means that the medfly (Ceratitis capitata Wiedemann) is present in the orchard.

The Black Fig Fly is very greedy of the fresh latex drop which forms on the ripe fig surface through the medfly eggs-laying hole, but it is also attracted to it when it has dried.
 

Medfly laying eggs in a ripe fig, causing a latex oozing.

 

Medfly laying eggs in a ripe fig, causing a latex oozing.
 

Below, two photographs showing black fig flies consuming fresh latex that oozes through medfly eggs-laying holes.

We note that the fig is not yet really ripe, but it has considerably softened.
 

Black fig flies sucking latex on a softened almost ripe fig.

 

Black fig flies sucking latex on a softened almost ripe fig.
 

As the medfly frantically attacks figs as soon as they begin to soften, it is not uncommon to see black fig flies consuming fresh latex on almost completely green figs.

But these figs have began to soften, mandatory condition for the medfly eggs-laying (which causes the latex oozing) to be possible.

In the two photographs below, we note that the fig ostiolar region has changed color.
 

A black fig fly sucking latex on a softened almost green fig.

 

A black fig fly sucking latex on a softened almost green fig.

 

FEEDING ON OTHER PLANTS THAN THE FIG TREE

Silba adipata McAlpine only lays eggs under the ostiolar scales or in the ostiolar canal of unripe figs. And the larvae of this species only feed and develop inside figs.

The Silba adipata McAlpine adults feed on the Fig tree (leaves, branches of the year, ripe figs), but they also feed on other plants.

Here are some observations that I have found in the specialized literature.

Fillipo SILVESTRI indicates in his masterful study of the Black Fig Fly (1917) that the adult of the species "feeds on sugary substances which it can find on trees".

The author does not specify which trees they are.

Reference : SILVESTRI F., 1917, Sulla Lonchaea aristella Beck. (Diptera : Lonchaeidae) dannosa alle infiorescenze e fruttescenze del caprifico e del fico, Bollettino del Laboratorio di Zoologia Agraria in Portici, vol.12, pp. 123 -146.

Nihat SCHEWKET, who studied the Black Fig Fly in the early 1930s in Western Anatolia (Turkey), says that "black fig flies like to lick the sweet things they can find in nature, such as the honeydew of the cochineal Ceroplastes rusci L. or that of aphids, and the juice of ripe or rotten fruits".

He adds further in the article that "black fig flies remain motionless on ripe figs and lick their tender, torn skin. This is also the case with other fruits"

Reference : SCHEWKET N., 1934, Die Feigeninsekten und die wesentlichsten Ursachen der Feigenfruchtfaüle, Anzeiger für Schädlingskunde, 10 (10), 118-119 (article for sale here).

Jean GHESQUIERE, a Belgian entomologist, studied the Black Fig Fly in the south of France at the end of the 1940s.

He specifies that the females "gorge themselves abundantly with fermenting fruits and sweet matter during the first ten days of their life, that is to say before their sexual maturity".

I note that the author designates fruit trees when he mentions fruits in fermentation, but he does not specify which species they are.

He also indicates that he observed black fig flies on fig tree twigs attacked by mealybugs of the species Ceroplastes rusci L., in search of the sugary excretions of these.

Reference : GHESQUIERE J., 1949, La mouche noire des figues Lonchaea aristella Beck. à la Côte d'Azur, comptes rendus des séances de l'Académie d'agriculture de France, T. 35, pp. 650-653.

B. I. KATSOYANNOS studied large black fig flies populations in 1981 and 1982, in the Chios island (Greece).

He reports that in August 1982, when the figs were not yet ripe, he often observed black fig flies feeding on, or in, the flowers of an ornamental climbing plant, trumpet jasmine (Tecoma radicans Juss.), located about 50 m (164ft) from the fig trees.

During the same period, he also observed black fig flies on citrus and olive trees in the region.

Reference : KATSOYANNOS B. I., 1983, Field observations on the biology and behavior of the black fig fly Silba adipata McAlpine (Diptera, Lonchaeidae), and trapping experiments, Z. ang. Entomol. 95, pp. 471-476.

A. M. TALHOUK, cited by B. I. KATSOYANNOS in the aforementioned article, mentions that the Black Fig Fly has been observed feeding on exudates of a cochineal (Ceroplastes rusci L.) and of other insects, as well as sweet juice from ripe figs later in the season.

Reference : TALHOUK A. M., 1969, Insects and mites injurious to crops in Middle Eastern Countries, Hamburg und Berlin, Paul PAREY

Bernard PEYRE, who is one of the main contributors to the present website, reported to me a personal observation of Black Fig Fly feeding elsewhere than on the fig tree. In August 2019, in the region of Béziers (France), he observed on a peach tree located a few meters from fig trees a black fig fly which was sucking aphids honeydew on the upper side of a leaf.

I have no personal observations about the Silba adipata McAlpine adult feeding on other plants than the Fig tre, but I observed it several times feeding on my garden table during my meals.

 

OBSERVATIONS OF BLACK FIG FLIES INVITING THEMSELVES TO MY TABLE

I have never seen Silba adipata McAlpine on plants other than the Fig tree.

However, I can report occasional observations outside the Fig tree, which were all made during meals on my terrace or in my garden, in the same area. This is the front area of the house, while my fig trees are all located at the back of it, about 20 m (66ft) away.

In September 2017, a black fig fly landed on a dish of figs of various varieties placed on my garden table, when I was finishing lunch under an olive tree. It only stayed a few seconds on the figs.

On July 2, 2018, it was during a dinner on my terrace that a black fig fly landed on the piece of bread placed next to my plate. This time too, the fly only stayed a few seconds. I had observed its characteristic approach flight near the piece of bread.

On July 8, 2018, a black fig fly appeared at my table on the terrace at the end of dinner, around 7:30 p.m. It did not land 30 cm away from me like that of the previous time, but really the farthest from me on the edge of the table. I then moved my chair 50 cm back, acting gently, and the fly was about 1.5 m away from me.

I was careful not to make any sudden movements, and it stayed for more than ten minutes, slowly moving around the top of the table while licking it. I noticed that it did not stop at the bread crumbs littering the table.

The black fig fly did not come near me. I found its behavior nervous. It took shelter several times under the table top, twirling with its very brisk jerky flight in short zig-zags, and reappeared each time slowly walking on the top of the table. I was able to take some photographs from a distance, but it did not let me approach the camera, a sign that it was not calm.

Below, a photograph showing a black fig fly licking the surface of my garden table (July 8, 2018).

A black fig fly licking a garden table.

On August 24, 2020, around noon, I finished my lunch taken in the shade of a silky oak (Grevillea robusta A. Cunn. ex R.Br.), about 6 m from the terrace where I made some of the previous years observations, when a black fig fly appeared a few inches above the table.

It landed in front of me and moved around, licking the surface of the table, but without paying attention to the bread crumbs. And it did not approach me, remaining on the edge of the table in front of my place.

It then began to fly around the armrests of one of the unoccupied armchairs around the table, and landed on one of the armrests. It went back and forth between the surface of the table, lingering to lick it, and the armrests for about a quarter of an hour.

Below, a photograph showing a black fig fly licking the surface of my garden table (August 24, 2020).

A black fig fly licking a garden table.

At one point, it approached a fork on the table and, with a short flight, it landed on one of its teeth and started to lick it. I immediately made the connection with the dessert (a flambé crepe with rum), the traces of which on the fork attracted the fly. It stayed on the fork about one minute, then definitively left the table.

Below,

One photograph showing a black fig fly licking the surface of my garden table, near a fork.

And the other showing a black fig fly licking a fork tooth (wings pointing down), attracted by the traces of a flambé crepe with rum.

A black fig fly licking a garden table.

 

A black fig fly licking a fork tooth.

I wondered if the sugar and rum combination could be an effective attractant for Silba adipata McAlpine. The next day, I had lunch in the same place, and I put aside on the table a small plate on which I had spread a mix of powdered sugar and rum. But I did not detect any presence of black fig flies. Neither during the meal, nor during a one hour observation after the meal, having left the plate alone on the table, and sitting 2 m away.

 

Retour début article Summary

 

FIGS INFESTATION

 

POSSIBLE INFESTATION OF SPECIES CLOSE TO FICUS CARICA L.

I have no personal observations about the possible infestation by the Black Fig Fly of species very close to Ficus carica L. And the only reference that I have found in the specialized literature concerns Ficus pseudocarica Batt. and Trab.

Filippo SILVESTRI indicates that in Algeria this species is attacked by the Black Fig Fly.

Reference : SILVESTRI F., 1917, Sulla Lonchaea aristella Beck. (Diptera : Lonchaeidae) dannosa alle infiorescenze e fruttescenze del caprifico e del fico, Bollettino del Laboratorio di Zoologia Agraria in Portici, vol.12, pp. 123 -146.

Note : F. SILVESTRI gave this species the Latin designation of the time, at least as he had understood it. When I read his masterful study, I could not find in the taxonomic databases whether this designation corresponds to Ficus pseudocarica Miq., which is currently considered in these databases a synonym of Ficus palmata Forssk. I think it is highly probable.

 

FIG INFESTATION CHECKING

To check if a fig has been attacked by the Black Fig Fly, how many Black Fig Fly eggs have infested a fig, and to determine if several females have attacked a fig, we must examine the underside of the ostiolar scales, and (if the ostiole has sllightly widened) the ostiolar canal.

The empty eggs envelopes (chorions) remain intact up to several months after the eggs-laying. We can find under the ostiolar scales of an overripe fig that dropped off the tree chorions of eggs laid three months before, when the fig was tiny and at the unripe stage.

Photograph 1 : 2 eggs of Silba adipata McAlpine under a reddish ostiolar scale of an unripe fig.
 

Black Fig Fly (Silba adipata McAlpine) : two eggs under an ostiolar scale of an unripe fig.
 

Below, photograph 2 : 5 chorions (empty eggs envelopes) of Silba adipata McAlpine under a reddish ostiolar scale of an unripe fig.
 

Black Fig Fly (Silba adipata McAlpine) : five chorions under an ostiolar scale of an unripe fig.
 

Below, photograph 3 : detachment of an ostiolar scale covering 3 empty eggs envelopes -chorions - (research under stereomicroscope in a reddened unripe fig dropped to the ground).
 

Black Fig Fly (Silba adipata McAlpine) : three chorions under an ostiolar scale of an unripe fig.

 

USING AN EMERGENCE BOX FOR IDENTIFYING THE INFESTATION

The Black Fig Fly (Silba adipata McAlpine) is the only pest that attacks UNRIPE figs, and the exit holes that we can observe on unripe figs are characteristic of this species.

An examination of the ostiolar scales and the ostiolar canal with a stereomicroscope, looking for chorions (empty eggs envelopes), will give us the confirmation that the fig is infested by the Black Fig Fly.

It is possible to visualize the species which infests the unripe figs, by putting them in an emergence box, after having checked the absence of exit holes.

The well developed larvae will rapidly abandon the figs. We can also directly place in the box well developed larvae that we found. In both cases, we will first get pupae, then imagos (I regularly observe a ten days time for the imagos releases, in summer).

For the emergence box, I use a medium-sized plastic freezer box, covered by a transparent food film held by an elastic.

To prevent the larvae and the pupae from drying out, I keep the emergence box out of direct sunlight.

Below, two photographs showing an emergence box inside which two Black Fig Fly imagos have been released.

We note that the hard green unripe fig has dried out, and we can see four pupae (two of which are open...).
 

Emergence box inside whih two Black Fig Fly imagos have been released.

 

Emergence box inside whih two Black Fig Fly imagos have been released.
 

It is rather easy to get Black Fig Fly imagos in an emergence box, but all the infested figs without exit holes do not result in imagos releases.

In some cases, pupation does not normally proceed. In others cases, the pupa looks normal but never opens. And sometimes, the imago fails to completely extract itself from the pupa and it dies.

Below, photograph 1 : results of Black Fig Fly pupations which failed in the emergence box.
 

Results of Black Fig Fly pupations which failed.
 

Below, photograph 2 : dead Black Fig Fly imago which did not succeed in completely extracting itself from the pupa and died. We note that only the head is outside the pupa.

The yellowish ptilinum residue, not retracted in the head, shows that the imago is dead. If it had been alive and emerging, the ptilinum would have been swollen and enormous.
 

Dead Black Fig Fly imago, partially emerged from the pupa.

 

PUPAE INSIDE UNRIPE FIGS

We can observe Black Fig Fly pupae (one, sometimes two) inside unripe figs. But, with the exceptions of a few varieties, it is very rare to make such an observation.

Below, two photographs sent to me by Bernard PEYRE, one of the permanent contributors to the present website.

The pupa was initially located in the central cavity of the fig. I note that the unripe fig bears two larvae exit holes, and I do not explain why one of the larvae did not abandon the fig and performed its pupation inside it.

I can simply relate this observation to two observations of a well-developed larva that I found dead in an unripe fig gallery, very close to an exit hole that the larva had not used. Would some well-developed larvae no longer have enough strength to come out the fig, and either die or begin their pupation ?
 

Black Fig Fly (Silba adipata McAlpine) : larvae exit holes on an unripe fig.

 

Black Fig Fly (Silba adipata McAlpine) : pupa inside an unripe fig.

 

DEAD IMAGOS INSIDE UNRIPE FIGS

I perform my regular observations (every year) of Black Fig Fly desiccated imagos in ripe figs of the 'Bourjassotte Noire' variety (main commercial fig cultivar in France). I buy these figs in the local markets, not growing this variety in my orchard, so I was not able to observe dead intact imagos inside unripe figs of this varriety.

With the varieties that I grow, I have no such observations either.

But Alain COSTA, who is one of the permanent contributors to the present website, observes from time to time dead intact Black Fig Fly imagos inside unripe figs of the variety 'Colar de Albatera' (commercial orchards).

He sent me the two photographs below.

I note that the imago which has emerged fom the pupa died in the central cavity of the unripe fig before having (even partially) deployed its wings. The wings have not even started to swell. This is a clue from which to deduce that the imago died very quickly after emerging from the pupa.
 

Dead Black Fig Fly imago inside an unripe fig.

 

Dead Black Fig Fly imago inside an unripe fig.

 

DEAD IMAGOS PARTIALLY EMERGED FROM PUPAE INSIDE UNRIPE FIGS

Sometimes, inside an unripe fig, the imago fails to completely extract itself from the pupa and it dies.

The photograph below shows two dead Black Fig Fly imagos partially emerged from pupae, found in an unripe fig ('Colar de Albatera’ variety).

For the individual for which the focus is sharp, the head and most of the thorax are outside the pupa.

And the yellowish ptilinum remainder, not retracted in the head, shows that the imago is dead. If it had been alive and emerging, the ptilinum would have been swollen and enormous.

Photograph credited to Alain COSTA, who is one of the permanent contributors to the present website.
 

Two dead imagos, partially emerged from pupae (unripe fig).

 

PUPAE AND DESICCATED IMAGOS INSIDE RIPE FIGS

Below, two photographs showing Black Fig Fly pupae and desiccated imagos inside ripe figs ('Bourjassote Noire' variety ; early harvest period).

We can note that a pupa found in a ripe fig results from an egg laying performed at least 11 - 12 days before (eggs incubation : 3 days + larva full development : 6 to 7 days + pupa formation : 2 days). For an empty open pupa, this minimal time becomes 18 - 20 days, as we consider the nymph full development duration (9 to 10 days), instead of the 2 days for the pupa formation.

In both cases, if we compare with the number of days required for the fig to reach the maturity stage from the unripe stage, we deduce that the egg laying has been performed at the unripe stage of the fig.
 

Black Fig Fly (Silba adipata McAlpine) : pupae and desiccated imagos inside ripe figs.

 

Black Fig Fly (Silba adipata McAlpine) : pupae and desiccated imagos inside ripe figs.
 

Below, two photographs showing Black Fig Fly desiccated imagos that I found inside ripe figs ('Bourjassote Noire' variety ; early harvest period).

The imagos have dried out in the unripe fig after emerging from the pupa inside it.

They are visible as large black dots within the softened infrutescence of the ripe fig, most often close to the open pupa in which they have developed.
 

Black Fig Fly (Silba adipata McAlpine) : desiccated imagos inside ripe figs.

 

Black Fig Fly (Silba adipata McAlpine) : desiccated imagos inside ripe figs.

 

DEAD IMAGOS PARTIALLY EMERGED FROM PUPAE INSIDE RIPE FIGS

Sometimes, inside the fig, the imago fails to completely extract itself from the pupa and it dies.

And we can find inside the ripe figs dead Black Fig Fly imagos partially emerged from pupae.

We must note that a failed imago emergence from a pupa found in a ripe fig results from an egg-laying performed at least 18 to 20 days before (eggs incubation : 3 days + larva full development : 6 to 7 days + nymph full developpement : 9 to 10 days – summer durations).

If we compare with the number of days required for the fig to reach the maturity stage from the unripe stage, we deduce that the egg-laying has been performed at the unripe stage of the fig.

The two photographs below show a dead Black Fig Fly imago partially emerged from the pupa, in a ripe fig ('Bourjassotte Noire’ variety). Only the head and one paw are outside the pupa.

The fact that the visible part of the imago is not fresh indicates that also the failed emergence occurred at the unripe stage of the fig.
 

Dead imago partially emerged from a pupa (ripe fig).

 

Dead imago partially emerged from a pupa (ripe fig).

 

BLACK FIG FLY INFESTATION AND FIG CONSUMPTION

It is important to keep in mind that infested ripe figs are a limited negative phenomenon.

According to my observations, they only represent 2 to 5 % of the harvested figs, depending on the varieties. And of this small percentage, a large part are imperceptible to the consumers.

I know from experience that very small larvae (2 - 3 mm ; 0.08 - 0.11’’) are imperceptible when eating a ripe fig infested by the Black Fig Fly, and I presume that pupae and dead imagos are also imperceptible (taking into account their tiny size and the fact that they are immersed in the infrutescence).

I think that the only figs with an unpleasant taste are those which have a rotten interior, due to a fly attack (Black Fig Fly, Medfly…) or a pathogenic fungi attack. However, it may be that when the infrutescence deterioration by the larvae reaches a certain level the taste slightly changes. But I am not really motivated to perform the test.

The general public does not know anything about the Black Fig Fly, even its existence. So, figs consumers do not cut and open figs and most often eat the rare infested ripe figs whitout noticing it.

Regarding the figs producers, ripe figs with larvae exit holes are discarded during harvest or manual quality control preceding the packaging stage.

And, knowing that all the infested ripe figs are attacked by the Black Fig Fly in the unripe stage (most often several weeks before the maturity stage), we can note that a well done prophylactic removal of the infested unripe figs on the tree eliminates the possibility of harvesting infested ripe figs.

Personally, until ten years ago, I had never opened a fig before eating it. But when the figs damages due to the Black Fig Fly significantly increased, and I observed that a small part of the infested unripe figs did not drop off the tree and reached the maturity stage, I started to systematically examine the inside of the figs before eating them.

Now, after having studied and photographed in close-up all the variants and détails of Black Fig Fly internal figs damages, psychologically I can no more eat a fig without cutting and opening it, in the field or at home.

And remenbering all what I saw in the ostiole under the stereomicroscope, also for psychological reasons, I felt obliged to cut the ostiolar region too (which I did not regret, because it is tasteless and has a coarse texture).

Gradually, as I was to cut and cut, I got into the habit of also cutting the tasteless neck of the fig.

This could be considered (ironically or not) as a certain « art of fig consumption ».
 

Black Fig Fly : fig consumption.

 

Black Fig Fly : fig consumption.

 

Retour début article Summary

 

POSSIBLE CONFUSION WITH A PATHOGENIC FUNGI ATTACK

 

In a ripe fig, a pathogenic fungi (molds type) attack is often confused with internal damages of Black Fig Fly larvae.

Pathogenic fungi attack : internal rot results from the development within the fig of molds type lower fungi (lower fungi include molds and yeasts). The spores at the origin of these fungi were introduced into the fig trough the ostiole via the wind or via various insects penetrating in the ripe fig (Blastophaga psenes, Drosophila species, ants…), or sucking in its ostiolar canal (flies, butterflies…). The interior of the ripe fig brings together the necessary conditions for the fungi development, in particular : water, sugar and heat.

In France, a specific pathogenic fungi attack, which regularly occurs on certain fig varieties only at their early harvest period, is called by the figs producers " la maladie de la fièvre" (the "fever disease").

In the orchards affected by the "fever disease", the producers make the first ripe figs of the season drop off the trees.

First criterion for distinguishing Black Fig Fly damages from molds type fungi attack : in case of a Black Fig Fly attack, we must find at least one chorion (empty egg envelope) when we examine the underside of the ostiolar scales, and the ostiolar canal, of the spoiled ripe fig (this examination is only easy and reliable when using a stereomicroscope).

Second criterion for distinguishing Black Fig Fly damages from molds type fungi attack : a fungi attack changes the color of the infrutescence (yellowhish, then brown, then blackish), but the fuits are not altered.

Below,

Two photographs showing internal rot of ripe figs, due to a molds type fungi attack (not a Black Fig Fly one) - 'Bourjassotte Noire' variety figs affected by the "maladie de la fièvre" ("Fever disease"), at its early harvest period (September).
 

Internal rot of a ripe fig, due to a molds type fungi attack.

 

Internal rot of a ripe fig, due to a molds type fungi attack.

 

SUPPLEMENT 1/4

Rot inside a ripe fig infested by the Black Fig Fly at the unripe stage.

The risk of confusion of a pathogenic fungi (molds type) attack with internal damages of Black Fig Fly larvae is amplified by the fact that a part of the infested ripe figs have also internal rot (on the same fig tree).

Below, two photographs of a second crop fig of the biferous variety 'Grise de La Saint-Jean', which was infested by the Black Fig Fly at the unripe stage, and which has reached the maturity stage with an interior partially rotten.

Note the larvae exit holes on the skin of the ripe fig, in the photograph 1.

Note that the infrutescence is not wholly rotten, in the photograph 2.

It should be emphasized that a significant part of the ripe figs infested by the Black Fig Fly do not show internal rot.
 

Ripe fig infested by the Black Fig Fly.

 

Rotten interior of a ripe fig infested by the Black Fig Fly.
 

For the 'Grise de la Saint-Jean' variety, the infested unripe figs which reach the maturity stage represent every year approximately 5 % of all ripe figs harvested on the tree.

If we want to check that the ripe fig was infested at the unripe stage : for this variety, the ripeness level shown by the photographs has been reached within 4 days from the unripe stage ; the presence of the larvae exit holes allows us to date the eggs-laying at at least 9 to 10 days (eggs incubation : 3 days + larvae full development : 6 to 7 days). We can deduce that the eggs-laying was performed at the unripe stage, at least 5 to 6 days before the unripe fig began to soften.

In fact, according to my observations, for most of the infested figs which reach the maturity stage instead of dropping off the tree, the eggs-laying is performed several weeks before the maturity stage (the record time that I observed was an eggs-laying carried out 2.5 months before the maturity stage, with a breba fig of the 'Grise de la Saint-Jean' variety).

 

SUPPLEMENT 2/4

Illustrations of the second criterion for distinguishing Black Fig Fly damages from molds type fungi attack : a fungi attack changes the color of the infrutescence (yellowhish, then brown, then blackish), but the fuits are not altered.

Below,

Photograph 1 : yellowish infrutescence of a ripe fig, at the beginning of a molds type fungi attack.

Photograph 2 : a brown fruit of a ripe fig, consecutively to a molds type fungi attack.

We can note in both photographs that the ripe fig fruits are not altered by larvae bites (no Black Fig Fly attack).
 

Yellowish infrutescence of a ripe fig, at the beginning of a molds type fungi attack.

 

A brown fruit of a ripe fig, consecutively to a molds type fungi attack.

 

SUPPLEMENT 3/4

Illustrations of Black Fig Fly larvae damages in a ripe fig ('Bourjassotte Noire' variety).

Below,

Photograph 1 : Black Fig Fly larvae damages inside a ripe fig.

Photograh 2 : details of Black Fig Fly larvae damages inside a ripe fig.

These illustrations allow us to see the state of the fruits altered by the Black Fig Fly larvae bites.

But we can note that, in this case, there is no risk of confusion with a molds type fungi attack, because the fig central cavity is not invaded by rot, contrary to what we see in the second photograph provided above in the supplement 1.
 

Black Fig Fly larvae damages inside a ripe fig.

 

Black Fig Fly larvae damages inside a ripe fig.

 

SUPPLEMENT 4/4

Gallerie traces in a rotten ripe fig infested by the Black Fig Fly.

If the rot degree inside a ripe fig is high, it is impossible to ckeck if the infrutescence has been altered by Black Fig Fly larvae bites.

The first clue to look for is the existence of larvae exit holes on the surface of the fig. But they are often difficult to spot on a ripe fig skin.

A second clue can be useful : galleries traces in the softened parenchyma of the ripe fig.

Below,

Photograph 1 : interior of a rotten ripe fig showing larva gallery traces in the upper part of the softened parenchyma, close to the ostiole.

Photograph 2 : detail of the larva gallery trace, for the right half of the fig in the first photograph.

If we cannot spot any larvae exit holes or galleries traces, and it is important to determine wether the Black Fig Fly has infested the fig (first appearance in the orchard), it is necessary to look for possible chorions (empty eggs envelopes) under the ostiolar scales and in the ostiolar canal (preferably using a stereomicroscope).

Knowing that, if we do not find any chorions, it is a simple pathogenic fungi attack.
 

Black Fig Fly : interior of a rotten ripe fig showing larva gallery traces.

 

Black Fig Fly : interior of a rotten ripe fig showing a larva gallery trace.

 

Retour début article Summary

 

LIFE CYCLE DURATION / LIFE SPAN

 

LIFE CYCLE DURATION

I have only partial personal observations for the biological durations forming the life cycle of the Black Fig Fly, and they match with those given by Filippo SILVESTRI in its masterful study of the Black Fig Fly (morphology, biology, fig infestation...), published in 1917.

Reference : SILVESTRI F., 1917, Sulla Lonchaea aristella Beck. (Diptera : Lonchaeidae) dannosa alle infiorescenze e fruttescenze del caprifico e del fico, Bollettino del Laboratorio di Zoologia Agraria in Portici, vol.12, pp. 123 -146.

Filippo SILVESTRI (1873-1949), was an entomology professor at the university of Roma, associate entomology professor at the Minnesota university, and director of an agrarian zoology institute near Napoli.

Having verified with my observations most of the F. SILVESTRI study informations (not only for the life cycle), I am confident in the informations given by the author that I have not yet personaly verified.
 

According to F. SILVESTRI, the biological durations for the Black Fig Fly are as follows.

Egg incubation (time between the egg-laying and the larva birth) : 3 days in summer, 8 days in April.

Complete larva development (life time of the larva inside the fig) : 6 to 7 days in summer, 24 days in April.

Complete nymph development (life time inside the pupa, before the imago emergence) : 9 to 10 days in summer (confirmed by my own observations), 16 days in April.

Thus, the duration of one life cycle is : 18 to 20 days in summer, 48 days in April.

Note : The F. SILVESTRI biological observations were performed in the Napoli region (Italy). Depending on warmer or cooler climatic conditions of the region where the orchard is located, they may be shorter or longer.
 

I add that, according to the F. SILVESTRI biological durations, for the Napoli region, the time between the eggs-laying and the larvae exit holes appearance is 9 to 10 days in summer, 32 days in April (egg incubation + complete larva development).

And, according to my personal observations, for the Toulon region, the larvae exit holes appearance occurs 11 to 26 days after eggs-layings performed during the first half of june (uniferous variety 'Bellone'), and 30 to 40 days after eggs-layings performed in April (breba figs of the 'Grise de la Saint-Jean' variety).
 

Below, two photographs of the end of a biological phase of the Black Fig Fly life cycle.

Photograph 1 : the larva abandons the fig after a development of 6 to 7 days inside it (in summer) - the egg-laying occurred 9 or 10 days before.

Photograph 2 : the youg imago has just emerged from the pupa, after a development of 9 to 10 days inside it (in summer). The egg-laying occurred 18 to 20 days before (the imago is not yet black-colored and its wings are not yet deployed ; the ptilinum is not yet retracted in the head).
 

Black Fig Fly (Silba adipata McAlpine) : fully developed larva abandoning the fig.

 

Black Fig Fly (Silba adipata McAlpine) : young imago recently emerged from the pupa.

 

LIFE SPAN

When I bred black fig flies, in my first years of studying the species, I had not the idea of trying to assess their life span. I just kept adults for a week fed with fig juice, not needing a longer period for my ex situ photography sessions and experiments.

But two authors give an estimate of the Black Fig Fly life span.

Jean GHESQUIERE, a Belgian entomologist, kept adult black fig flies alive for six weeks in the laboratory, fed with grape juice. It ensures that in situ the adult life span is much longer.

Reference : GHESQUIERE J., 1949, La mouche noire des figues Lonchaea aristella Beck. à la Côte d'Azur, comptes rendus des séances de l'Académie d'agriculture de France, T. 35, pp. 650-653.

Filippo SILVESTRI, in his masterful study of the Black Fig Fly, indicates that the adult lives one month or more.

Reference : SILVESTRI F., 1917, Sulla Lonchaea aristella Beck. (Diptera : Lonchaeidae) dannosa alle infiorescenze e fruttescenze del caprifico e del fico, Bollettino del Laboratorio di Zoologia Agraria in Portici, vol.12, pp. 123 -146.

I therefore retain the estimate of 1.5 to 2 months for the life span of Silba adipata McAlpine.
 

Below, two photographs illustrating the Black Fig Fly life.

Photograph 1 : a black fig fly in its approach flight to join four others on a fig tree branch of the year.

Photograph 2 : four black fig flies consuming latex on attachment points of torn fig tree leaves petioles.

Note : in both cases, the four or the five flies represent the totality of the Black Fig Fly individuals of the fig tree, grouped together on a very small area by the strong attractiveness of the latex.
 

Black fig Fly approach flight.

 

Four black fig flies consuming fig tree latex.

 

Retour début article Summary

 

MATING

 

MATING OBSERVATION

During my many years of observing and studying black fig flies, I have been able only once to see two of them mated (June 30, 2016, around noon, as I was walking around an old tuft of the 'Dauphine' variety with ripe breba figs).

I could observe the mated flies for about a minute on a leaf upper side. To my relative surprise, while being mated they were feeding on a puddle of ripe fig juice that had fallen from a fig above.

The coupling position was of the end-to-end type. The two flies were placed at the same level in opposite directions and were joined by the end of their abdomen.

One of the two having the wings open and raised, the other the wings closed. In the photographs, I determined that the male was the individual with raised wings, and I confirmed that the other was the female.

Below, a photograh and its enlargement showing the two mated black fig flies.

In the photograph enlargement, we can identity the male (open raised wings) by its narrow interocular space, and the identification of the female is confirmed by its tightly segmented abdomen end.

Black fig flies mating on a fig tree leaf.

 

Silba adipata McAlpine mating on a fig tree leaf.
 

The two flies did not move on the puddle of sweet juice at the usual speed of a single fly, but performed slow circular movements almost in place while keeping the wings in the same position.

The two bodies joined by the abdomen were most often found in the continuation of one another (photograph below).
 

Black fig flies in copula on a fig tree leaf.
 

But, sometimes, the movement made them shifted relative to each other, with an angle of an amplitude never larger than 45 ° (photograph below). 
 

Silba adipata McAlpine mating on a fig tree leaf.
 

After about a minute, the male fly turned around and went up the leaf, towards the edge of it, seeming to drag the female who kept the wings closed and who was still in the extension of the male abdomen. I could not determine if the female was really being dragged or if it was walking backwards.
 

Two mated black fig flies going up a fig tree leaf.
 

Arrived at the edge of the leaf a few centimeters higher than the initial location, the male fly placed its wings flat and in a cross, the female keeping the wings folded.
 

Two mated black fig flies on the edge of a fig tree leaf.
 

Then the male took off, the female still attached to it. I am sure the couple did not split up when they took off. And it seemed to me that only the male was flying and that the female had remained with its wings closed, the body in the extension of that of the male. I had the impression that a rigid bar was flying away.

I am comforted in my impression by the report of similar observations for other Diptera found on the Internet, in which the mated female remains joined to the male in flight but without flying, ballasting the latter.

I was not able to observe the black fig flies couple beyond the takeoff, due to the still very fast flight of the male, and despite half an hour of meticulous scrutiny of the fig tree tuft, I could not find the mated flies on the tree or observe them in flight.

Below, two photographs showing the male and female positions on the edge of the fig tree leaf, just before the male took off with the female still attached to it.

We note the well developed last abdominal segment of the male, appearing under the closed wings of the female.
 

Two mated black fig flies on the edge of a fig tree leaf, just before taking off.

 

Two mated black fig flies on the edge of a fig tree leaf, just before taking off.

 

WHERE DOES SILBA ADIPATA McALPINE MATING TAKE PLACE ?

In my many years of intensive observations on various fig trees, at all periods of the season and at any times of the day, I have been able only once to see two mated black fig flies (see above).

I am therefore convinced that mating of Silba adipata McAlpine does not occur on fig trees, and that mated flies of this species only very rarely land on these.

I have not found in the specialized literature any information on the mating place of the Black Fig Fly.

For instance, B. I. KATSOYANNOS studied in 1981 and 1982 large populations of black fig flies in the island of Chios (Greece), and he explicitly specifies that he did not observe mating in fields.

Reference : KATSOYANNOS B. I., 1983, Field observations on the biology and behavior of the black fig fly Silba adipata McAlpine (Diptera, Lonchaeidae), and trapping experiments, Z. ang. Entomol. 95, pp. 471-476.

A plausible hypothesis is that Silba adipata McAlpine mating could occur in the air, while the flies are flying.

Aerial swarming in insects is generally a mating activity, characterized by pair formation in flight.

Numerous references, among which I cite : SULLIVAN Robert T., 1981, Insect Swarming and Mating, The Florida Entomologist, vol. 64 (1), pp. 44–65.

J. F. McALPINE and D. D. MUNROE have described the swarming behavior for 16 species (which do not include Siba adipata McAlpine) of the Lonchaeidae family.

Reference : McALPINE J. F., MUNROE D. D., 1968, Swarming on Lonchaeid flies and others insects, with description of four new species of Lonchaeidae (Diptera), The CanadianEntomologist, vol.100, pp. 1154-1178.

With respect to the Lonchaeidae family, the authors believe that, in general, swarming probably facilitates the discovery of mate. But they state that they have little or no evidence to support this belief, and that the possibility that the Lonchaeidae mates meet at places other than the swarm must certainly be considered.

And they specify that female lonchaeids occur very rarely if ever in the swarm, and that no matings were ever observed in any lonchaeid swarms.

I only know one reported swarm observation for Silba adipata McAlpine. It was made on August 20, 1982 by B. I. KATSOYANNOS, while he was studying Lamprolonchaea smaragdi Walker swarming in the Chios Island (Greece).

Reference : KATSOYANNOS B. I., 1983, Swarming of Lamprolonchaea smaragdi Walker (Diptera, Lonchaeidae) and a few other Diptera observed in Chios, Greece, Bulletin de la Société Entomologique Suisse, vol. 56, pp. 183 -185.

And I have no personal observation of Silba adipata McAlpine swarms.

Nevertheless, I regularly observe black fig flies groups flying between two trees in a similar way than that of the swarm described by B. I. KATSOYANNOS. I do not qualify them as aerial swarms because these groups only involve two to three specimens.

The group performs repetitive flights, more or less on the horizontal plane and limited to an elliptic space, with an amplitude of about 2 m (6.5 ft), at a height of about 1.5 m (5 ft). The aerial group is rather stationary, but Inside the group the flies permanently keep their very fast zigzaging characteristic flight pattern.

I can observe this phenomenon for long whiles, sometimes more than one hour, in the late afternoon, at dusk.

Over the season, I regularly perform this type of observations at two places : between my ‘Bellone’ variety fig tree and an oriental persimmon (in June), and betweem an olive tree and a silky oak, near a hedge, at 30 m (100 ft) from my fig trees (during certain periods of summer).

I think that these black fig flies grouped in the air are males waiting for females, or males and females just before mating (or mating).
 

 

Retour début article Summary

 

BLACK FIG FLY LARVA

 

SOME INFORMATIONS TO FAMILIARIZE US WITH THE LARVA

The larva is formed of 11 segments (3 for the thorax, 8 for the abdomen), plus a cephalic capsule (head) which is retractable inside the first thoracic segment.

In the photograph 1, below, the cephalic capsule is not visible, because its is retracted inside the first thoracic segment. The latter is easily recognizable having a different pointed shape compared to the other segments - on the right in the photograph.

In the photograph 2, below, the tiny cephalic capsule is visible, protuding from the first thoracic segment - on the right in the photograph. It is not visible to the naked eye.

On the last segment of the larva, we can see two brown dots, which are respiratory orifices called the posterior stigmas - on the left in the photographs. They are not visible to the naked eye.

Inside the two first thoracic segments, we observe by transparency a black Y-shaped anatomical piece composed of the pharyngeal armature extended by the mandibles, at the end of which are two mouth hooks - on the rigth in the photographs.

The pharyngeal armature is a skeleton on which certain muscles are attached, in particular those of the pump which sucks food.

According to my measurements, the length of the larva is a little less than 1 mm (0.038’’) at birth, and about 7 mm (0.28’’) at full development (when it leaves the unripe fig).

Knowing that when we cut and open an old infested fig, the largest larvae are most frequently 6.5 mm (0.26’’) long, not having completed their development.

Below, two photographs of the Black Fig Fly larva.
 

Black Fig Fly (Silba adipata McAlpine) larva (dorsal view).

Black Fig Fly (Silba adipata McAlpine) larva (lateral view).

 

LARVA : THE MOUTH HOOKS

Below, two photographs showing the two mouth hooks, at the end of the mandibles.

Note : in the photograph 1, the larva appears to have a rather long appendix at the end of which are the mouth hooks. It is not the cephalic capsule. It is the lateral view of the first thoracic segment, recognizable by the black pharyngeal armature inside it. The cephalic capsule is the tiny part beginning at the level of the small black ball at the base of the mouth hooks.
 

Black Fig Fly (Silba adipata McAlpine) larva : the two mouth hooks.

 

 Black Fig Fly (Silba adipata McAlpine) larva : the two mouth hooks.

 

LARVA : VENTRAL SURFACE OBSERVATION

The ventral surface of the larva is characterized by the presence of creeping welts (fleshy transverse ridges), which assist it in its movements.

Below, a photograph showing the ventral surface of a Silba adipata McAlpine larva.

From left to right in the photograph, three features can be highlighted, as follows.

The ventral surface of the three first segments (thorax) is smooth, they have no creeping welts.

The creeping welts of the eight abdominal segments are located on their anterior part, and are increasingly big from the first to the last of them.

The last segment shows two protuberances : a creeping welt in its anterior part, and the anal area in its posterior part. The anal area is circular and has several lobes.
 

Black Fig Fly (Silba adipata McAlpine) larva ventral surface (creeping welts).

 

LARVA : THE RESPIRATORY SYSTEM

The mature larva has two pairs of spiracles (respiratory orifices) : an anterior pair, and a posterior pair. The newly born larva has only two spiracles (the posterior ones).

The anterior spiracles are located on the first thoracic segment (in its posterior part, at the limit with the second segment). The posterior spiracles are located on the upper part of the posterior surface of the larva.

Each spiracle consists of an atrium which opens to the exterior and a chitinized internal structure.

Two dorsal longitudinal trunks (main tracheas) extend between the anterior and posterior spiracles (one on each side).

From the main tracheas, a complex tracheal branches network supplies air to the muscles and the internal organs.

Below, four photographs showing details about the Black Fig Fly larva respiratory system.
 

Photograph 1 : the four spiracles are visible.
 

Black Fig Fly (Silba adipata McAlpine) larva : the four spiracles.
 

Photograph 2 : we can follow the left main trachea from the left anterior spiracle to the left posterior one.
 

Black Fig Fly (Silba adipata McAlpine) larva : main tracheas.
 

Photograph 3 : we can see the exact location of the left anterior spiracle on the first thoracic segment. We can follow the main trachea starting from it, to join the posterior spiracle (not visible).
 

Black Fig Fly (Silba adipata McAlpine) larva : main tracheas.
 

Photograph 4 : some ramifications of the right main trachea are visible.
 

Black Fig Fly (Silba adipata McAlpine) larva : main tracheas ramifications.

 

Retour début article Summary

 

BLACK FIG FLY PUPA

 

HOW DEEP ARE THE BLACK FIG FLY PUPAE IN THE SOIL ?

For those who would imagine Black Fig Fly control means destroying the pupae, or killing the nymphs inside the pupae, it is useful to know how deep are the pupae in the soil.

I have observed the difficultty for the larvae to burrow into the soil depending on its texture, but I have no personnal observations about the burrying depth.

Two authors give a response.

Filippo SILVESTRI, in its masterful study of the Black Fig Fly (morphology, biology, fig infestation...), published in 1917, indicates that the larvae burrow to a depth of 0.80 to 4" (2 to 10 cm), before starting their pupation.

Reference : SILVESTRI F., 1917, Sulla Lonchaea aristella Beck. (Diptera : Lonchaeidae) dannosa alle infiorescenze e fruttescenze del caprifico e del fico, Bollettino del Laboratorio di Zoologia Agraria in Portici, vol.12, pp. 123 -146.

Nihat SCHEWKET, who studied the Black Fig Fly in eastern Anatolia (Turkey), in the early 1930s, specifies for his part that the larvae burrow to a depth of 1.20 to 1.60" (3 to 4 cm), before starting their pupation.

Reference : SCHEWKET N., 1934, Die Feigeninsekten und die wesentlichsten Ursachen der Feigenfruchtfaüle, Anzeiger für Schädlingskunde, Vol. 10, Issue 10, pp. 118-119 (article for sale).

Below, a photograph showing a young imago having emerged from the pupa and reached the surface of the soil. Note that the wings are not yet fully swollen to their maximal length, whereas the upper thorax is already black-colored - we can deduce that the imago came out the pupa at least one quarter of an hour ago.
 

Black Fig Fly (Silba adipata McAlpine) : young imago emerged from the soil.

 

PUPA SIZE AND COLOR

Photograph 1 : three Black Fig Fly pupae.
 

Three Black Fig Fly pupae.

 

Photograph 2 : the Black Fig Fly pupa is 4 mm long.
 

Black Fig Fly (Silba adipata McAlpine) : pupa size.

 

Photograph 3 : the Black Fig Fly pupa changes color as the nymph develops (first whitish, than light brown, and dark brown when the nymph is almost completly developed).
 

Black Fig Fly (Silba adipata McAlpine) : pupa color.

 

PUPA OPENING

The pupa opens under the push of the imago ptilinum. The opening is made according to preformed dehiscence lines delimiting a cap which opens like a cover.

Below, two photograhs showing  empty pupae found in the soil.
 

Black Fig Fly (Silba adipata McAlpine) : empty pupa found in the soil.

 

Black Fig Fly (Silba adipata McAlpine) : empty pupa found in the soil.

 

IDENTIFYING THE BLACK FIG FLY PUPA COMPARED TO THAT OF THE MEDFLY

Having simultaneously bred medflies (Ceratitis capitata Wiedemann) and black fig flies (Silba adipata McAlpine), I have been able to compare the pupae of the two species.

With practice, we easily recognize each other.

The pupa of Silba adipata McAlpine clearly appears smaller and less rounded than that of Ceratitis capitata Wiedemann.

The latter is slightly longer, much wider, and it generally has a greater width to length ratio.

Below, two photographs showing the differences between Ceratitis capitata Wiedemann pupae (on the left in the photographs) and Silba adipata McAlpine ones (on the right in the photographs).
 

Black-Fig-Fly pupae (on the right) and Medfly pupae (on the left).

 

Black-Fig-Fly pupae (on the right) and Medfly pupae (on the left).

 

Retour début article Summary

 

CONTROL METHODS

 

THREE BASIC ACTIONS AGAINST SILBA ADIPATA McALPINE

The three basic actions that I perform every year against Silba adipata McAlpine are as follows.

1. Prophylactic removal on the tree of the infested figs (as soon as possible, before the appearance of the exit holes ; daily inspection). The collection of the infested figs on the ground is inefficient (when the attacked fig drops off the tree, the larvae have already abandoned it, with the exception of rare figs in which a part of the larvae are still present). When well done,this process ensures that zero larva will reach the ground.

2. One McPhail trap baited with water solution of ammonium sulfate (4 %) on each fig tree. As soon as the fig tree vegetation visibly starts : the first of March in my orchard ; we must not wait the figs, the Black Fig Fly is present in the orchard before the breba figs.

3. One McPhail trap baited with water solution of ammonium phosphate (4 %) on each fig tree as soon as the appearance of the Medfly (Ceratitis capitata Wiedemann), June 30 in my orchard.

I keep the two traps on the fig tree until the harvest of the last ripe fig. If we want to continue with a prophylactic action (it is only an option), we can keep the ammonium sulfate trap (not the other) on the fig tree until the end of december (the Black Fig Fly is generally still present in the orchard to feed, even if there are no figs and no leaves on the fig tree).

IMPORTANT : the two traps may be insufficiently effective depending on three factors : the place of the orchard in the region affected by the Black Fig Fly, the varieties of the fig trees, and the level of actitvity of the Black Fig Fly for a given year. But I did not find a better solution (for my orchard), although my numerous traps experiments. I suggest the test of the process on one or two fig trees for verifying that the results are sufficient in the local specific conditions of the orchard and for the grown varieties, and not to immediatlly generalize it..

I only deal with amateur's orchards. In the commercial orchards, from a certain number of hectares, there is a mass effect which allows the traps to have a better (but still partial) effect on the Black Fig Fly control. This is to be determined with the local phytosanitary authorities.
 

Photograph 1 : McPhail trap hung in a fig tree.

Photograph 2 : ammonium sulfate attractant.
 

A McPhail trap hung in a fig tree against the Black Fig Fly (Silba adipata McAlpine).

 

Ammonium sulfate  : a food attractant for the Black Fig Fly (Silba adipata McAlpine).
 

The two traps on each fig tree have two roles : they allow the capture of a certain number of Silba adipata McAlpine individuals coming to feed on the fig tree, and they continuously provide me with the indication of the pest pressure level in my garden.

But they are clearly insufficient to significantly limit the loss of figs crop.

To compensate for the insufficient effectiveness of the traps, after having tested various means of fight without success, I chose the figs individual bagging (organza bags).

 

PROPHYLACTIC REMOVAL OF THE INFESTED FIGS

Prophylactic removal of the infested figs must be carried out on the tree (not on the ground - the infested figs fallen on the ground contain less than 5 % of the larvae), before the appearance of the larvae exit holes (for this : daily to weekly inspection).

This process ensures that no larva will reach the ground, thus that there will never be pupae in the soil for the whole orchard.

Regarding the supposed overwintering in the soil, I think that we do not know if the Black Fig Fly (Silba adipata McAlpine) overwinters as a pupa in the soil, or if it overwinters as an imago (diapause). The arguments which make me adopt a cautious approach on this subject are exposed in the "Cycle de vie" chapter, "Hivernation" subchapter).

I personnaly have no opinion on which of the two hypotheses might be correct. But even if it is the hypothesis of the pupae in the soil, the prophylactic removal of infested figs of the last crop of the orchard eliminates the possibility to have any pupa in the soil during the winter season.

I do not know a (soaking or other) method for killing the larvae (before the pupation) or the nymphs (inside the pupae) in the soil, that could significantly save work time compared to the prophylactic removal of infested figs on the tree. Altough, for killing the nymphs in the pupae, I had a particular interest in a possible biological control process (Pachyneuron vindemmiae Rondani), that I expose at the end of this chapter.

There are two limits to the prophylatic removal : the fig trees which are so high that a part of the figs are unattainable, and the fig trees of light-skinned varieties, for which the detection of theattack before the appearance of the first exit hole is almost impossible.

In the South of France, these limits do not really exist because all the commercial cultivars and the main valuable cultivars foramateurs are dark-skinned. And the fig trees in the commercial orchards and in the majority of the amateurs' orchards are trained in rather compact trees (3-4 m high), in order to permit the harvest from the ground, without using a ladder.

Note : prophylactic infested figs removal comes up againt the difficulty of extending the method to the whole area affected by the Black Fig Fly. I regularly practice this process that ensures that there is never pupae in the soil of my whole orchard. However, I observe every year in my orchard a high level of back fig flies presence, uniquely due to flies coming from the neighborhood. But my action contributes to lower the general pressure of the Black Fig Fly, especially during the season.

Below, two photographs showing the results of prophylactic infested figs removal, carried out in organic farmers' orchards.

They are credited to Margaux ALLIX, who is one of the permanent contributors to the present website.
 

Using prophylactic infested figs removal against the Black Fig Fly.

 

Using prophylactic infested figs removal against the Black Fig Fly.

 

FIGS INDIVIDUAL BAGGING
 

Method choice

Figs bagging prevents the Black Fig Fly female from depositing its eggs under the ostiolar scales of the unripe fig.

Protecting the goups of unripe figs on the twigs of the year with large organza bags, or an organza veil tied to the twig, gives very good results - if some leaves are cut.

This method was reported to me by Rueben CHATCUTI, a reliable correspondent who applies it in Malta (as does one of his friends in Israel), and who sent me the photograph below (espaliered fig tree).
 

Figs group protected against the Black Fig Fly with organza.
 

But I was never motivated for experimenting this process, because it seems insufficiently practical to me, in my orchard conditions. But I might be wrong...

I apply the figs individual bagging method (wilth small rigid organza bags), that I think more practical and which requires an acceptable processing time in the amateur orchard.

One of the reasons why I have chosen figs individual bagging is that I must keep the protection when the figs soften, and when they are ripe, in order to (partially) protect them against the medfly (Ceratitis capitata Wiedemann), very active in my region. The individual protection facilitates the harvest, staggered for each branch.

The photograph below shows a group of individually bagged figs in my orchard (the internodes are almost nonexistent).
 

Individually bagged figs against the Black Fig Fly.
 

Bags specifications

The organza must be sufficiently rigid to keep the black fig fly which lands on it far enough from the fig ostiole.

The resistance to the sun is an important criterion, and it must be appreciated and tested according to the desired durability of the bag : single use, or reusable for one or several seasons.

I am aware that a weave size allowing pollination is important for certain fig growers in California, but my task is simplified because in France this criterion does not exist. The commercial fig cultivars and the thirty best fig varieries for the garden or the amateur’s orchard produce fruits through parthenogenesis. Even for the fig trees collectors, the percentage of Smyrna or San Pedro type varieties is almost negligible. Moreover, Blastophaga psenes L. is not present in 75 % of the French territory where it does not withstand the winter climatic conditions, whereas the fig tree is grown by the hobbyists in all the French regions.

I think that the choice of a bag with two draw strings is imperative. Care must be taken to choose a closure with a satin ribbon, and not with a little cord that, even if it is thin, thickens the part of the bag which must be inserted between the fig and the leaf petiole.

For the moment, the two draw strings closure seems to meet the specifications, but testing is still ongoing.

An elastic strip would be another possible solution for the individual fig bag closure system. According to my measurements, the fig neck has an average diameter of 0.20" (5 mm) when the unripe tiny fig reaches the diameter from which it can be attacked by the Black Fig Fly (about 0.40" - 1 cm). I do not know anything about sewing, but I suspect a technical difficulty...
 

Figs critical diameter 

For being really efficient against the Black Fig Fly, we must act with precision.

The fig diameter which must trigger bagging is 0.40’’ (1 cm).

Taking into account that the smallest size that I observed for an attacked fig is a diameter of 0.43" (1.1 cm).

And that, according to my measurements, about 40 % of the Black Fig Fly attacks occur on figs with a diameter from 0.43 to 0.55’’ (1.1 to 1,4 cm).

My figs individual bagging tests are still ongoing.

In practice, I will start bagging when the five biggest figs on the tree will have reached the critical diameter (like I do for for starting the eggs-laying observation campaign on a given fig tree).

Using, of course, a vernier caliper to exactly measure the figs diameters (the syconium not being a regular sphere, I usually measure its largest diameter).

And I will include in the first bagged figs batch all those the neck of which is sufficiently individualized.

Below, two photographs showing a Black Fig Fly female laying eggs under an ostiolar scale of a tiny unripe fig.

Note, particularly in the photograph 1, the size difference between the unripe figs.
 

Black Fig Fly female laying eggs under an ostiolar scale of a tiny unripe fig.

 

Black Fig Fly female laying eggs under an ostiolar scale of a tiny unripe fig.
 

Processing time

My large-scale tests show that, working at a normal speed, I can individually bag 80 figs in one hour with small organza bags (easy and difficult to access figs, on the same 4 m high tree, bagged from the ground without recourse to a ladder).

This make it possible to save in 5 hours of work the whole of a fig tree bearing 400 figs, which constitutes a significant crop for a single tree with pedestrian harvest.

This processing time is quite acceptable in an amateur garden with a small number of fig trees, knowing that, given the fig tree way of fruiting, the workload can be spread over a few days.

Note.

To bag an isolated and well-placed fig, the time is less than ten seconds, which could lead to a processing time of 6 figs per minute, or 360 figs per hour. But to process the whole of a tree 3 to 4 meters high, we have to take into account the movements around the tree and the branches handling, as well as various difficulties to place the organza bags on the figs.

The three main ones are: figs high up or in the center of the tree, which require bringing the branch towards us and holding it with one hand, which is also used for bagging ; figs tightly grouped because internodes are practically non-existent ; terminal figs of the branch which are stuck to the apical bud, between which and the fig we have to insert the bag.

Thus, at normal processing speed, necessary because with raised arms it can sometimes be a hard work, I could not do better than 80 figs per hour (average productivity for a whole fig tree).

Below, two photographs illustrating figs individual protection against the Black Fig Fly, with small organza bags.
 

Figs individual bagging against the Black Fig Fly.

 

Figs individual bagging against the Black Fig Fly.

 

SPRAYING INSECTICIDE AGAINST THE BLACK FIG FLY

In France, according to the European Union phytosanitary regulations, and the French ones which can be more restrictive, the only active substance which can be used for sprays against fruit flies on the fig tree is Deltamethrin - 15 g/l.

Commercial products : Decis Protech (Pearl Protech, Split Protech) of Bayer SAS ; and its generics Decline 1.5 EW (Jabal), and Deltastar (Vivatrine EW).

This chemical is prohibited for the amateurs' orchards and for the professional organic figs producers. It is uniquely used by the non-organic professional figs producers.

It is the most widely used control method against the Black Fig Fly in the commercial orchards. According to the figs producers with whom I am in contact, it gives good results : it does not eliminate crop losses, but it significantly reduces them.

The regulatory dosage is 0,083 l/hl, and the last treatment must be carried out at least 14 days before the harvest. Maximum authorized for the season : 3 treatments.

Note : an agricultural engineer consultant told me that for the product to be really effective against the Black Fig Fly, it is imperative to perform a sequence of three immediatly consecutive treatments in the season. I cannot, of course, verify this information.
 

Below, two photographs showing very rare observations of 6 black fig flies being on a fig tree at the same time.

I usually observe 1 to 3 black fig flies on one fig tree, 4 to 5 at certain periods in the season. I only observed twice the presence of 6 black fig flies, and once the presence of 7 of these. The flies have been gathered using latex oozings on a fig tree twig of the year(photograh 1), and on a fig tree leaf petiole (photograph 2).
 

Black Fig Fly (Silba adipata McAlpine) : six flies on a fig tree twig of the year.

 

Black Fig Fly (Silba adipata McAlpine) : six flies on a fig tree leaf petiole.

 

USING INSECTICIDE TRAPS AGAINST THE BLACK FIG FLY

In France, according to the European Union phytosanitary regulations, and the French ones which can be more restrictive, there are only four insecticide traps which can be used against fruit flies on the fig tree.

They are uniquely authorized for the professional figs producers (they are prohibited for the amateurs’ orchards).

Commercial names : Vio-trap ; Decis Trap DS ; Flypack suzukii ; Flypack Ficus.

They are ready-to-use-traps, intended to be hung in the tree without any preparation (single use).

Note : the four traps can be used by the organic figs producers.

Vio-Trap (of DAKOFAKA) : the trap contains 0,125 g/kg of deltamethrin and 21 g/kg of hydrolyzed proteins. Autthorization date : June 15, 2013. It exists two versions of this trap : the green one (for the olive fly), and the yellow one (initially intended for the medfly) – the figs producers use the yellow version.

Decis Trap DS (of BAYER SAS) : the trap contains 0,015 g of deltamethrin and three food attractants (acetoin, methional, ethyl acetate). It exists several versions for the Decis Trap, note that it is the DS one, recently authorized (June 14, 2021).

Flypack suzukii (of SEDQ) : the trap is designed for Drosophila suzukii Matsumura control. We must prefer the Flypack Ficus trap, marketed by the same company for the Silba adipata McAlpine control..

Flypack Ficus (of SEDQ) : the trap contains 0,015 g of deltamethrin and two diffusers (food attractant and hexanol). Recently authorized (April 15, 2021). The inner surface of the transparent trap cover is impregnated with the insecticide.

This trap has been specifically designed for the Silba adipata McAlpine control by the SEDQ spanish company. It has been tested in the main French commercial figs orchards by the figs producers association « AOP Figue de Solliès ».

The tests, which were carried out under the control of the regional agricultural technical service, show that using this trap reduces the crop damages by 50 %.

Implementation rules by the « Figue de Solliès » producers : 80 traps/ha, early June, duration of use : 120 days.

Note : Spinosad (well known and efficient product for the organic growers) is not authorized in France for the fig tree. An authorization request is being prepared for the European Union phytosanitory authorities by an association of organic figs producers of the southwest French region.
 

Below, photograph1 : "Vio-trap" trap model on a fig tree (credit : figs producers association « AOP Figue de Solliès »).
 

Black Fig Fly (Silba adipata McAlpine) : insecticide trap "Vio-trap".
 

Below, photograph 2 : "Flypack Ficus" trap model on a fig tree (credit : municipal newspaper of the city of Solliès-Pont).
 

Black Fig Fly (Silba adipata McAlpine) : insecticide trap "Flypack Ficus".

 

EXPERIMENTING GLUE AND LATEX ASSOCIATION AGAINST THE BLACK FIG FLY

I have tested glue (two kinds) on leaves, cut petioles, twigs of the year (with a protective middle layer), and on micro-traps made with small beekeeping equipments - always in association with fig tree latex as a food attractant.

I also tested the glue directly applied on, or around, latex oozings on the fig tree.

None of these methods has been effective against the Black Fig Fly.

The latex seems to be less attractive than when naturally oozing on fig tree branches ; in addition, one of the tested glue kinds seems to be sometimes repellent ; the other is insufficiently strong (the Black Fig Fly can walk on it, altough with difficulty, reaches a branch without glue and flies off the fig tree).

And, when directly applying glue on, or around, latex oozings on branches, I observed that the Black Fig Fly approaches the sticky area, but is careful to never enter it despite the presence of the latex.

Note : I have never used (nor considered using) the glue for sealing the ostioles because it is a dangerous and illegal product if it is put in contact with a fig. All the experiments I have carried out strictly comply with the European Union directives related to the "direct food contact‘’.

Below,

Photograph 1 : first used glue kind - Tangle-Trap anti insects glue, in the form of a tube gel (which I spread with a rubber kitchen spatula).

Photograph 2 : second used glue kind - Protecta Rampastop Natura natural tree glue (organic farming), in the form of a paste in a metal tin (which I first spread with a rubber spatula, but I found it better to use a toothbrush).
 

First kind of glue experimented against the Black Fig Fly.

 

Second kind of glue experimented against the Black Fig Fly.

 

EXPERIMENTING GLUE AND LATEX ASSOCIATION AGAINST THE BLACK FIG FLY - EXAMPLE 1

Glue (Tangle-Trap) + fig tree latex + petioles cut into pieces - on fig tree leaves.

Implementation : a layer of glue on the upper side of a vertical large leaf + fresh latex from the base of four torn petioles spread over the glue + one (or two) petiole(s) used for the latex cut into pieces stuck on the glue, to enhance the trap attractiveness.

Results : no insect captures during the long observation session that followed the trap implementation. Then, daily trap inspection during 10 days : 4 insects captured during the first 3 days (including two flies, but no Silba adipata McAlpine individuals), and no other captures during the remainder of the period.
 

Using glue and latex association against the Black Fig Fly.

 

Using glue and latex association against the Black Fig Fly.

 

EXPERIMENTING GLUE AND LATEX ASSOCIATION AGAINST THE BLACK FIG FLY - EXAMPLE 2

Glue (Protecta - Rampastop Natura) + fig tree latex - on cut fig tree leaves petioles.

The petiole is cut to three quarters of its length.

Implementation : latex influx at the petiole top + a layer of glue on the petiole + fresh latex from the base of two torn petioles spread over the glue, by small touches.

Results : no insect captures during the long observation session that followed the trap implementation. Then, daily trap inspection during 10 days : one Silba adipata McAlpine individual captured the day after the trap implementation, and no other captures during the remainder of the period.
 

Using glue and latex association against the Black Fig Fly.

 

Using glue and latex association against the Black Fig Fly.

 

EXPERIMENTING GLUE AND LATEX ASSOCIATION AGAINST THE BLACK FIG FLY - EXAMPLE 3

Glue (Tangle-Trap) + fig tree latex + two latex oozing points - on.a fig tree branch of the year.

Implementation : a layer of glue on a terminal portion (4’’ ; 10 cm) of a fig tree branch of the year (without intermediate support for the glue) + fresh latex from the base of four torn petioles spread over the glue + two latex oozing points created in the sticky portion by tearing two leaves (to enhance the trap attractiveness).

Note : direct appication of the glue on a branch is prohibited by the instructions for use, and, from experience, I know that it causes significant necrosis, due to the combined action of the glue and the sun. But, I decided to sacrifice for the test the top of the branch of the year.

Observation.

The trap was implemented at 3 p.m., and from 3 p.m. to 8 p.m., no black fig flies (or other insects) landed on the sticky area.

At around 8 p.m., a black fig fly directly landed on it, just above the lowest latex oozing point. As soon as it came into contact with the glue, it tried to fly away by vigorously beating its wings, but it did not succeed. It then began a slow walk on the glue up the branch, with difficulty.

Below, two photographs showing the black fig fly walking up the sticky fig tree branch of the year.

In the second photograph, we note that two paws on the left side are stuck to each other.
 

Black fig fly walking up the sticky fig tree branch of the year.

 

Black fig fly walking up the sticky fig tree branch of the year.
 

The black fig fly thus climbed several centimeters on the glue to the highest latex oozing point, below which it consumed latex for a few moments. I wonder how it did not stick its proboscis to the glue... But at its scale the latex layer constituted a mass of significant volume above the glue (photograh below).
 

Black fig fly on a sticky fig tree branch of the year, consuming latex brushed above a layer of glue.
 

Then, the black fig fly walked very slowly back down the sticky branch to the height of the petiole of an untorn leaf located between the two latex oozing points (photograph below).
 

Black fig fly walking on a sticky fig tree branch of the year.
 

It reached the petiole, which was carrying traces of glue only at its beginning (photograph below).
 

Black fig fly escaping the glue spread over a fig tree branch of the year.
 

After a 0.8’’ (2 cm) course on it, having escaped the glue, it sharply flew away (without difficulty, in one movement).

Below, a photograph showing the black fig fly having escaped the glue and getting ready to fly away.
 

Black fig fly having escaped the glue and getting ready to fly away.
 

I noted in the photographs of the black fig fly which escaped the glue that two paws on the left side are stuck to each other.

The following photographic enlargement makes this clearly appear.
 

Black fig fly having escaped the glue with two paws stuck to each other.
 

After this observation, I performed a daily inspection of the trap for 10 days : 3 insects captured, but no black fig flies. Although I observed that three black fig flies daily frequented the concerned fig tree, mainly in the late afternoon.

Conclusion.

The Tangle-Trap glue in tube gel form used in the trap had no repellent action for Silba adipata McAlpine.

Regarding the Black Fig Fly ability to walk on the sticky branch : the latex layer may have decreased the stickiness of the glue by mixing with it, or the fly may have moved over the latex layer, which remained on top of the glue one, partially playing the role of a barrier in relation to it.

As it is, the experimented trap associating Tangle-Trap glue and latex seems ineffective in combating Silba adipata McAlpine.

 

EXPERIMENTING GLUE AND LATEX ASSOCIATION AGAINST THE BLACK FIG FLY - EXAMPLE 4

Glue (Tangle-Trap) on a transparent adhesive tape + fig tree latex + two latex oozing points - on.a fig tree branch of the year.

Implementation : transparent adhesive tape rolled up on a 2.5’’ (6 cm) long portion of a fig tree branch of the year + a layer of glue + fresh latex from the base of four torn petioles spread over the glue + two latex oozing points created by tearing off two leaves (to enhance the trap attractiveness).

Note : the presence of adhesive tape under the glue layer avoids a branch necrosis, due to the combined action of the glue and the sun.

Below, a photograph showing the transparent adhesive tape used for the trap.
 

Transparent adhesive tape used in the trap against the Black Fig Fly.
 

The transparent adhesive tape was placed over the entire surface of two internodes surrounding a node carrying a leaf intended to be torn off to cause a latex oozing.

The trap was implemented at 3 p.m., and at 3:15 p.m., I caused a first latex oozing point, tearing off the leaf located just above the sticky area of the branch.

At 7 p.m., I created a second one by the same method in the center of the sticky area.

Below, a photograph showing the trap implemented against the Black Fig Fly (transparent adhesive tape + glue + latex + central latex oozing point).
 

Trap implemented against the Black Fig Fly.
 

Below, a photograph showing the latex oozing point in the center of the sticky trapped area.
 

Latex oozing point in the center of the sticky trapped area, against the Black Fig Fly.
 

Observation.

From 3 p.m. to 8:30 p.m., no black fig fly (or any other insect) landed on the sticky area. At 8:30 p.m., a black fig fly landed near the highest latex oozing point.

It stayed there for two minutes, consuming latex and moving around, but not descending into the sticky area, then it flew away. I realized that having created a latex oozing point above the trapped area had been a mistake. See the photograph below.
 

A black fig fly consuming latex above a sticky trapped area.
 

To prevent this situation from happening again, I covered with glue the entire top area of the branch, including this latex oozing point. And scalded by the failure of the trap reported in the example 3, I decided to add an excessively thick layer of glue on the initially deposited one.

A black fig fly appeared shortly after and directly landed in the middle of the trapped area, near the only latex oozing point left in the open. I figured that, like the one seen in the experiment reported in the example 3, it would not be able to fly away from the sticky area and I quite sharply brought my camera forward.

Immediately, the black fig fly took off, but in two stages : it was first retained by the paws which remained stuck to the layer of glue, but in the same movement it continued to vigorously beat its wings and it detached from the sticky branch.

After this observation, I performed a daily inspection of the trap for 20 days : 4 insects captured, but no black fig flies. Although I observed that three black fig flies daily frequented the concerned fig tree, mainly in the late afternoon.

Conclusion.

The Tangle-Trap glue in tube gel form used in the trap had no repellent action for Silba adipata McAlpine.

But this experimentation confirms the results of that reported in the example 3 : Tangle-Trap glue covered with a latex layer is insufficiently strong to retain a black fig fly which lands on the sticky area, making this type of trap ineffective in combating Silba adipata McAlpine.

Regarding the Black Fig Fly ability to fly away from the sticky branch, this experiment also shows that the thickness of the glue layer is not a parameter which can counterbalance the ineffectiveness of the glue. On second thought, this seems logical. The fly has a very low weight and has an extremely small contact surface with the glue (that of the terminal pads of the 6 paws ...). It does not sink into the glue, and thus walks on the surface of the glue layer regardless of the thickness of the latter.

I also keep in mind that the branch chosen for the trap must not have any latex oozing points located outside the trapped area, so as not to divert Silba adipata McAlpine from the trap.

 

EXPERIMENTING GLUE AND LATEX ASSOCIATION AGAINST THE BLACK FIG FLY - EXAMPLE 5

Natural tree glue Protecta Rampastop Natura (organic farming) + fig tree latex - in a micro-trap hanging in the fig tree.

Micro-trap concept.

I started from three Silba adipata McAlpine observations :

. The number of individuals of the species present at the same time on a fig tree is not high (from 1 to 3, sometimes 4 to 5, exceptionally 6).

. The attractiveness of pure fig tree latex is greater than that of the other food attractants (sugary substances, diammonium phosphate, ammonium sulfate, etc.).

. With a latex oozing point on a fig tree branch, I managed to group together 4 black fig flies over 4 cm2 and I attracted 6 over a 4'' (10 cm) length.

I deduced that it would be better to prioritize experimentations with pure fig tree latex as food attractant, and that it might not be necessary to implement large traps, but rather micro-traps.

After considering the constraints to be met for the micro-traps (volume, possibility of hanging or fixing horizontally on the branches, presence of a bottom to keep the latex), I opted for the use of beekeeping equipment (bee water feeder, queen bee cage…).

Implementation.

A short bee water feeder suspended by a galvanized wire of 1.5 mm diameter and 12” (30 cm) long, covered with glue (except for micro-perforations on one side), and containing pure latex obtained by tearing off six fig tree leaves, brushed on the internal surface (bottom and sides).

Below, a photograph showing the components of the micro-trap.
 

Micro-trap used against the Black Fig Fly.
 

Observation.

When I hung the micro-trap at 6 p.m., the two black fig flies present on the fig tree ignored it, and after almost 3 hours of waiting, I began to think that the micro-trap was not attractive.

Below,

Photograph 1 : the glue-latex micro-trap hanging in the fig tree.

Photograph 2 : the sticky bee water feeder used  as a micro-trap.
 

Micro-trap used against the Black Fig Fly.

 

Sticky bee water feeder used as a micro-trap against the Black Fig Fly.
 

But, at 8:50 p.m., I spotted a Silba adipata McAlpine individual getting stuck on the micro-trap base, lying on its side and frantically wagging its paws in the air.

My attention having been temporarily taken up by another trap, I could not observe the fly landing, nor the way in which it started sticking its body.

On close examination, I noticed that the two wings were partially stuck, so that the flight would be impossible, and, with the help of my strong magnifier, I was able to determine that it was a male individual.

Below , two photographs showing the black fig fly captured with the glue-latex micro-trap.
 

A black fig fly captured by a glue-latex micro-trap.

 

A black fig fly captured by a glue-latex micro-trap.
 

It was the only capture of this micro-trap during the observation session, which was nearing the end.

After this observation, I performed a daily inspection of the micro-trap for 10 days : no other black fig flies were caught (only some tiny insects), although I observed that black fig flies daily frequented the fig tree.

Conclusion.

The Protecta Rampastop Natura glue used in the micro-trap had no repellent action for Silba adipata McAlpine.

But this experimentation confirms the results of those I previously reported : traps using glue and fig tree latex association are ineffective in combating Silba adipata McAlpine.

 

EXPERIMENTING GLUE AND LATEX ASSOCIATION AGAINST THE BLACK FIG FLY - EXAMPLE 6

A piece of a fig tree leaf petiole stuck with glue on a fig tree branch of the year + a layer of Tangle-Trap glue on the upper side and at the ends of the piece of petiole + a small mass of fresh latex (oozing from a torn petiole) deposited on the glue + a few touches of latex on either side of it.

Experimentation results : this trap, like the others using glue and fig tree latex association of which I reported the experimentation above, is not really effective in combating Silba adipata McAlpine.

Below, two photographs showing the trap.
 

Trap using glue-latex association against the Black Fig Fly.

 

Trap using glue-latex association against the Black Fig Fly.

 

EXPERIMENTING GLUE AND LATEX ASSOCIATION AGAINST THE BLACK FIG FLY - ADDITIONAL POSSIBILITIES

I tested several other micro-traps than the one presented in the example 5 of traps associating glue and fig tree latex (see above).

But only to evaluate their attractiveness for the Black Fig Fly (step 1), and not as part of an experiment with glue (which was to constitute the step 2).

This two-steps method finds its justification in the possibility of discovering the repellent character of the glue. The step 1 checks if the Black Fig Fly is attracted to the micro-trap. If so, if in step 2 it is no longer the case, we can suspect that this is due to the presence of the glue.

Given the discouraging results observed in previous experiments, I no longer prioritized the experiments with this type of traps and therefore did not carry out the step 2.

However, I think it could be useful to show the step 1 for some of these micro-traps, for those who would like to experiment them with glue (step 2) against the Black Fig Fly.
 

EXAMPLE 1

Implementation : galvanized wire of 1.5 mm diameter and 12” (30 cm) long + queen bee cage + absorbent paper for household use on which fresh fig tree latex has been deposited.

This micro-trap attracted one black fig fly during the observation session (3 hours). But the test was not continued the following days due to a lack of availability on my part.

Below, three photographs showing the micro-trap given as example 1.
 

A micro-trap against the Black Fig Fly.

 

A micro-trap against the Black Fig Fly.

 

A micro-trap against the Black Fig Fly.
 

EXAMPLE 2

Implementation : galvanized wire of 1.5 mm diameter and 12” (30 cm) long + queen bee cage + fig tree branches of the year and fig tree leaves petioles (all of them cut into more or less small pieces).

This micro-trap attracted up to two black fig flies at the same time during the observation session (3 hours). But the test was not continued the following days due to a lack of availability on my part.

Below, two photographs showing the micro-trap given as example 2.

We note a black fig fly licking the external surface of the queen bee cage.

Reminder : trap without glue, to test only its attractiveness in a first step.
 

Testing a micro-trap against the Black Fig Fly.

 

Testing a micro-trap against the Black Fig Fly.
 

Below, two photographs showing a black fig fly that landed on the queen bee cage (that will be covered with glue in the step 2 of the experiment).
 

A black fig fly on a micro-trap.

 

A black fig fly on a micro-trap.
 

Below, one photograph shows a black fig fly on the wood at the top of the micro-trap. And the other shows two black fig flies at the same place, one of them partially being on the queen bee cage.

The wood part of the micro-trap will not be covered with glue in the step 2 of the experimentation, but I have observed that the black fig flies easily move from the wood to the queen bee cage.
 

A black fig fly at the top of a micro-trap.

 

Two black fig flies on a micro-trap.
 

EXAMPLE 3

Implementation : a long bee water feeder horizontally fixed to a vertical fig tree branch of the year with a galvanized wire of 1.5 mm diameter, and containing fresh thin slices of a fig tree branch of the year.

This micro-trap attracted one black fig fly during the observation session (3 hours). But the test was not continued the following days due to a lack of availability on my part.

Below, two photographs showing the horizontal micro-trap given as example 3.

In one of the photographs, we note a black fig fly licking a wood slice, attracted to the latex smell.

Reminder : trap without glue, to test only its attractiveness in a first step.
 

Testing a horizontal micro-trap against the Black Fig Fly.

 

Testing a horizontal micro-trap against the Black Fig Fly.
 

A variant of the horizontal micro-trap consists in adding on the bottom and the edges of the bee water feeder fresh latex from the base of two torn fig tree leaves petioles.

Below, a photograph showing a black fig fly licking the fig tree latex added on the horizontal micro-trap.
 

A black fig fly licking fig tree latex added on a micro-trap.

 

OSTIOLE OBTURATION EXPERIMENTS

As I consider that traps baited with food-attractants have only a prophylactic role for the Black Fig Fly (see the "Attacks characteristics" chapter), I think that it is more efficient to try to prevent the female Black Fig Fly from laying eggs in the ostiole of the unripe fig.

I have published on the present website my experiments about ostiole obturation with self-adhesive etiquettes complying with the European Union directives relating to direct food contact. They are not at all stickers for children activities. They are fully food grade, and reserved for the fruits producers (to be directly put on fruits, with a logo or a customizable text). Thus, they are expensive, but their cost will significantly drop if their use becomes massive in the orchards.

Principles and specifications : page.

Experiment 1 : page.

Experiment 2 : page.

For the moment, I have not found a satisfactory solution, because the etiquette adhesive does not hold on the fig after a few hours or a few days, depending on the case, although the etiquettes are especially sold for being used on fruits (effectively, I tested them on various other fruits and there is no problems). The second photograph below shows an auto-adhesive etiquette which has peeled off the fig - a black fig fly is feeding on the upper side of the etiquette.

I think that there is is a probem of chemical incompatibility of the acrylic adhesive with the fig skin.

But the very positive result of my experiments is that for an amateur's orchard this method requires a quite acceptable processing time : 8 hours and 30 minutes (a day of work) to save 1000 figs (process at a normal speed).

So, it would be interesting to understand and to solve the chemical incompatibility.

And we have a precise and encouraging information about the processing time for other ostiole obturation methods of the same type that could be experimented.
 

Black Fig Fly (Silba adipata McAlpine) : ostiole obturation.

 

Black Fig Fly (Silba adipata McAlpine) : ostiole obturation.

 

USING YELLOW STICKY TUBES AGAINST THE BLACK FIG FLY

During my first years of fighting against the Black Fig Fly, in association with the prophylactic infested figs removal, I used sticky yellow tubes.

They are hollow plastic tubes, covered with glue and which contain a powdered food bait for Diptera (di-ammonium phosphate), the smell of which diffuses through three holes located in the top of the tube. It should be remembered that this is not a pheromone trap. The tube is provided at its top with a flexible hook by which it can be fixed to a small branch.

Implementation.

I systematically anticipated the Black Fig Fly attacks by placing the sticky tubes on fig trees from the beginning of March, knowing that the Black Fig Fly appears in my orchard during the first ten days of March. I did not take into account the presence or not of developed breba figs.

Regarding the use of the holes, I opened them to the maximum and no longer touched the setting.

I used one sticky tube per fig tree, about 2 m high and at the periphery, on a part of a branch well clear of the surrounding leaves (so as to prevent the tube from sticking to the leaves). I hung it on the fig tree side exposed to the east (because, according to my observations, the black fig flies often arrive from the east in my orchard).

I renewed the sticky tube when its surface was saturated, approximately every month (or even more quickly).

Selectivity and efficiency.

Regarding the yellow sticky tubes selectivity with respect to the Black Fig Fly, I observe that it is zero.

However, there is no bee catch, only a few wasps. Hornets are also caught, but they have the strength to loosen, even if they do so with difficulty.

In addition to black fig flies, it is mainly other flies that are caught, including fruit flies such as the Olive Fly (Bactrocera oleae Rossi), and the Mediterranean Fruit Fly (Ceratitis capitata Wiedemann).

When the yellow tube is loaded with flies, it is difficult to recognize the black fig flies which are stuck. When a dead black fig fly has kept its wings in their characteristic position (closed and overlapping), it is easier to identify it.

Regarding the sticky tubes efficiency, I observe that when a yellow sticky tube is placed on a fig tree, black fig flies get stuck on it, but I note that this does not prevent the permanent presence on the fig tree of one or more other black fig flies which feed without paying attention to the sticky tube, which in no way attracts them.

For Black Fig Fly eggs laying females, the protection of unripe figs by the sticky yellow tubes is null.

But this is the case for all traps (such as, for example, McPhail traps baited with ammonium sulfate). According to my observations, a female in need of eggs laying which arrives on a fig tree immediately begins to lay eggs in an unipe fig, then proceeds to a sequence of successive eggs layings (up to twenty visited figs), without interruptions, remaining exclusively concentrated on iits eggs laying task (not being attracted to any food source). At the end of the eggs layings sequence, it leaves the fig tree.

Conclusion.

I consider the yellow sticky tubes with food attractant as a way to limit the Silba adipata McAlpine pressure, but in no case to satisfactorily protect a fig tree crop against this pest.

I have replaced them by McPhail traps baited with a 4 % water solution of ammonium sulfate, which are significantly more efficient (even if they too constitute only a way of limiting the pest pressure).

Yellow sticky tubes were designed to combat the medfly, and it is in this use that it is best to implement them. However, even against the medfly I replaced them, and I use McPhail traps baited with a 4 % water solution of di-ammonium phosphate, which give better results.

Below, two photographs showing a yellow sticky tube used against the Black Fig Fly.
 

Yellow sticky tube used against the Black Fig Fly.

 

Yellow sticky tube used against the Black Fig Fly.
 

Below, two photographs showing a black fig fly stuck on a yellow tube, which has kept its characteristic wings position (closed and overlapping).
 

A black fig fly stuck on a yellow tube.

 

A black fig fly stuck on a yellow tube.
 

Below, two photographs showing black fig flies stuck on a yellow tube, which have not kept their characteristic wings position.
 

A black fig fly stuck on a yellow tube.

 

A black fig fly stuck on a yellow tube.

 

PACHYNEURON VINDEMMIAE Rondari : A NATURAL (BUT INSUFFICIENTLY HARMFUL) ENEMY FOR SILBA ADIPATA McALPINE

Filippo Silvestri (1873-1949), in its masterful study of the Black Fig Fly, indicates that he observed the presence in pupae of a tiny parasitoid hymenoptera (2 mm long), the name of which is Pachyneuron vindemmiae Rondani.

Reference : SILVESTRI F., 1917, Sulla Lonchaea aristella Beck. (Diptera : Lonchaeidae) dannosa alle infiorescenze e fruttescenze del caprifico e del fico, Bollettino del Laboratorio di Zoologia Agraria in Portici, vol.12, pp. 123 -146.

The author specifies that the female of this species searches for the Black Fig Fly pupae which are on the surface of the soil between the dropped figs, or those wich are poorly hidden at a little depth, and deposits one egg on the nymph (not in the nymph) inside the pupa.

But he considers that this species would be of negligible contribution in the Black Fig Fly control, because it cannot attack the almost totality of the pupae, wich are burried in the soil at 2-10 cm ( 0.8-4’’ ) depth. Moreover, F. Silvestri mentions that he only found Pachyneuron vindemmiae Rondani in the Portici and Resina localities, whereas he examined thousands of pupae collected in the Napoli, Salerno and Lecce regions, and more than 1000 pupae received from Tripoli.

I found also a more recent reference to this parasitoid hymenoptera : B. I . Katsoyannos, who studied large populations of black fig flies in the Chios Island (Greece), reports that he found (once only -September 27, 1981), among 70 collected pupae, 8 pupae of which emerged 8 specimens of the parasitoid species Pachycrepoideus vindemmiae Rondani (synonym of Pachyneuron vindemmiae Rondani).

Reference : KATSOYANNOS B. I., 1983, Field observations on the biology and behavior of the black fig fly Silba adipata McAlpine (Diptera, Lonchaeidae), and trapping experiments, Z. ang. Entomol. 95, pp. 471-476.

Below, a Pachyneuron vindemmiae Rondani female drawing, credited to Filippo Silvestri (see the F. Silvestri description).
 

Pachyneuron vindemmiae Rondani

 

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