Silba adipata McAlpine

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Author: François DROUET.
Photographs: François DROUET.
(unless indicated).
All rights reserved.

 

 

Biological control

 

 

 

It would be interesting to find parasitoids or predators to control Silba adipata McAlpine at certain stages of its life cycle. I report herafter the rare observations on this subject, but, as of the last modification date of this chapter (August 18, 2020), no species has been identified that could produce results large enough to halt the Silba adipata McAlpine.devastating action on immature figs.

 

F. SILVESTRI'S OBSERVATIONS

Filippo SILVESTRI, 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.

The larva emerging from this egg feeds on the pupa of the Black Fig Fly, and, after having fully developed, transforms into a pupa inside the Black Fig Fly pupa. Then, the adult Pachyneuron vindemmiae Rondani emerges from its pupa and that of the Black Fig Fly by piercing a hole with its mandibles.

The complete development of the parasitoid, from egg to adult, takes 15 days in summer, and 16 to 23 days from September to November.

F. SILVESTRI 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 depth. Moreover, he 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.
 

Pachyneuron vindemmiae Rondani

Pachyneuron vindemmiae Rondani (female specimen)
Credit: F. SILVESTRI - see
description.
 

F. SILVESTRI does not know of any other specific enemy to the Black Fig Fly, including any bacteria or fungi. He simply notes that the blastophage can be considered at the level of the caprifig tree as an indirect enemy of the Black Fig Fly. Indeed, the blastophage is at the origin of the transformation of the flowers into galls which completely fill the central cavity of the fig, which prevents the young larvae which are there from moving and causes their death.

 

B. I. KATSOYANNOS' OBSERVATIONS

I found also a more recent reference to this parasitoid hymenoptera.

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

 

E. TUTMUS' OBSERVATIONS

In his thesis relating to Silba adipata McAlpine, defended in 2013 at the University of Aydin (Turkey), Esref TUTMUS provides on page 32, § 4.5, some indications relating to the enemies of Silba adipata McAlpine. Reference: TUTMUS E., 2013, University Adnan MENDERES thesis  - Aydin (Turkey), Aydin ili incir bahçelerinde Silba adipata McAlpine (=Lonchaea aristella Becker) (Diptera: Lonchaeidae)'nin yayilisi, popülasyon degisimi ve zarar oraninin belirlenmesi, 44 p.

In 2011, no natural enemies of Silba adipata McAlpine were detected in figs. In 2012, parasitoid wasps and predatory ants were found. But the author does not provide any details, simply mentioning that an identification phase is underway.

 

J.H. GILIOMEE'S INDICATION

J.H. GILIOMEE et al. indicate that in South Africa, where Silba adipata McAlpine was identified in 2006 and 2007, no parasitoids were observed for the species.

Reference: GILIOMEE J. H., E. VENTER E., WOHLFARTER M., 2007, Mediterranean black fig fly, Silba adipata McAlpine (Diptera: Lonchaeidae), recorded from South Africa, African Entomology 15(2), pp. 383-384.

 

ANTS: OURS OBSERVATIONS

I have observed that the ants attack the eggs of Silba adipata McAlpine. They extract the eggs from the osiole of immature figs, after having shredded the ostiolar scales, most often in small groups.
 

Ant having extracted a Black Fig Fly egg fron the ostiolar scales,

Ant having extracted a Black Fig Fly egg fron the ostiolar scales.
 

Margaux ALLIX (Perpignan, France) and Alain COSTA (Albatera, Spain), two of the agonomists belonging to our small team, have observed that the ants attack the larvae of Silba adipata McAlpine.(when they have fallen to the ground, or when they are abandoning the immature fig).
 

Ant attacking a Black Fig Fly larva, which is abandoning the immature fig.

Ant attacking a Black Fig Fly larva, which is abandoning the immature fig.
Credt: Alain COSTA.

 

AAnt attacking a Black Fig Fly larva, which fell fom the immature fig to the ground

Ant attacking a Black Fig Fly larva, which fell fom the immature fig to the ground.
Credit: Margaux ALLIX
(CIVAMBIO 66).
 

Should we consider ants as regulators of the Black Fig Fly populations ? Certainly, but unfortunately in a very limited way because the percentages of Silba adipata McAlpine eggs and larvae removed by ants are very low.

 

 

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