Silba adipata McAlpine

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

 

 

Activity start and end in the year

 

 

 

According to the following plan: hibernation emergence date / first ovipositions, last ovipositions / last presence in the season.

 

HIBERNATION EMERGENCE DATE / FIRST OVIPOSITIONS

 

MY OBSERVATIONS (FIRST APPEARANCE IN THE YEAR)

The first Silba adipata McAlpine appearance in my garden (hibernation emergence) regurarly occurs during the first half of March (examples of first appearance dates: March 14  for 2016, March 10 for 2020, March 9 for 2021).

In order to determine the first appearance date, I implement at the begginning of March two surveillance processes: first, a McPhail-type trap on my 'Grise de la Saint-Jean' fig tree (aqueous solution of diammonium phosphate at 4%), and on my 'Bellone' fig tree (ammonium sulphate 4%); secondly, pieces of fig tree twigs debarked on the top and on one side (length 30 cm), which I place in the 'Bellone' variety fig tree area that black  fig flies usually frequent. The debarking allows the diffusion of latex smells very attractive for Silba adipata McAlpine, at a time when the fig tree leaves are not yet developed.

But, in several years of experience, I noted that it is not these processes that allow me to determine the hibernation emergence date. They give me the possibility of very early seeing for the first time of the year Silba adipata McAlpine individuals present in the garden (between March 20 and April 10), but it is a deduction that always gives me the first presence date of the species in my garden.

Indeed, I consider the earliest oviposition date that I have been able to determine, and I deduce the Black Fig Fly presence in my garden at least 10 days earlier (eggs maturation time, according to Filippo SILVESTRI). 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.
 

Debarked fig tree twigs placed on the target fig tree for Silba adipata McAlpine detection, in March 2021.

Debarked fig tree twigs placed on the target fig tree for Silba adipata McAlpine detection, in March 2021.
(in an usual frequentation area of a fig tree 'Bellone' tuft)
.

 

Silba adipata McAlpine first 2021 detection, with a debarked fig tree twig placed on a target fig tree.

Silba adipata McAlpine first 2021 detection, with a debarked fig tree twig placed on a target fig tree.

 

Silba adipata McAlpine: first 2021 catch, in a McPhail-type trap (aqueous solution of diammonium phosphate at 4 %).

Silba adipata McAlpine: first 2021 catch, in a McPhail-type trap (aqueous solution of diammonium phosphate at 4 %).

 

Silba adipata McAlpine: first 2021 catch, sexing and size measurement.

Silba adipata McAlpine: first 2021 catch, sexing and size measurement.
(note that the female individual covers 5 millimeter graduations, which is a large size for the species).

 

MY OBSERVATIONS (FIRST OVIPOSITIONS)

According to my observations and deductions, the first Silba adipata McAlpine ovipositions in my garden (Toulon region, France) take place during the second half of March, in the breba figs of my 'Grise de la Saint-Jean' variety fig tree (examples of first oviposition dates: March 24 for 2016, March 20 for 2020, March 19 for 2021).

It happens to me to be able to observe very early in the season egg laying females on this fig tree, but it is quite rare. Generally, I determine the earliest ovipositions using a method of ovipositions datation based on the infested figs examination (date of larvae exit holes appearance, or larvae sizes).
 

Silba adipata McAlpine laying eggs in an immature breba fig ('Grise de la Saint-Jean' variety).

Silba adipata McAlpine laying eggs in an immature breba fig ('Grise de la Saint-Jean' variety - second half of March.

 

Silba adipata McAlpine laying eggs under an immature breba fig ostiolar scale ('Grise de la Saint-Jean' variety).

Silba adipata McAlpine laying eggs under an immature breba fig ostiolar scale - second half of March.
 ('Grise de la Saint-Jean' variety).

 

REPORTS FROM OTHER OBSERVERS

In the Portici region, near Napoli, Filippo SILVESTRI observed that the first eggs are deposited the first half of April in the profichi of the caprifig trees. He indicates that fresh eggs can be found from May in the domestic fig trees figs. 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.

Concerning the beginning of the attacks in France, Louis TURINETTI indicates that in Menton larvae are found in infested figs from the month of May. Reference: TURINETTI L., 1921, Note sur la présence en France du Lonchaea aristella  Beck., Bulletin de la Société entomologique de France, pp. 195-196.

Alain COSTA mentions the first Silba adipata McAlpine flights appearance in February for the year 2019 in the Albatera region, in Spain (where are located large commercial fig trees orchards of the early biferous variety 'Colar de Albatera', the harvest start of which takes place around mid-May). Reference: COSTA A., 2019, El cultivo de la Higuera en el campo de Albatera, Newton publicaciones, page 133 (ISBN 978-84-943430-3-2, 183 pages).

 

LAST OVIPOSITIONS / LAST PRESENCE IN THE SEASON

 

MY OBSERVATIONS

The latest egg laying that I observed in my garden (Toulon region, France) 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 fact, an egg laying would be possible as long as it exists an immature fig on my 'Col de Dame Noire' fig tree, that is to say the last September week.

I do not take into account the last ripe figs presence, because Silba adipata McAlpine does not attack the softened figs at the maturity stage or just before (infested ripe figs are figs attacked at the immature stage which have continued their development until the maturity stage, despite the larvae activity inside them).

The last Black Fig Fly presence in my garden is much later than the possible last egg laying date. In 2017, I decided to leave my traps on the fig trees until December 31 to determine the last presence date. The last Silba adipata McAlpine individual was captured on November 20. I noted that the last ripe fig harvest in the garden 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 only feed and develop inside figs). I think my garden remains attractive late in the season for Silba adipata McAlpine because the ornamental plants it shelters are all evergreen (some even blooming in November), and that there are evergreen fruit trees bearing fruit until December (citrus fruits, feijoas, etc.).
 

Silba adipata McAlpine laying eggs under an immature fig ostiolar scale.

Silba adipata McAlpine laying eggs under an immature fig ostiolar scale.

 

REPORTS FROM OTHER OBSERVERS

F. SILVESTRI observed in the Portici region, 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 domestic fig trees figs 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 Silba adipata McAlpine adults catches 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), informed me that the latest Silba adipata McAlpine egg laying that he observed on his fig trees occurred on October 12, 2014, in mid-day, in an unripe fig of the 'Brown Turkey' variety.

Alain COSTA, agricultural engineer-consultant and fig producer, 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 on December, and he sent me two photographs of these figs taken on December 13, 2019 (see below).
 

Unripe figs of the 'Blanca' variety attacked by Silba adipata McAlpine - December 13, 2019.

Unripe figs of the 'Blanca' variety attacked by Silba adipata McAlpine - December 13, 2019.
 (credit: Alain COSTA).

 

Unripe figs of the 'Blanca' variety infested by Silba adipata McAlpine - December 13, 2019.

Unripe figs of the 'Blanca' variety infested by Silba adipata McAlpine - December 13, 2019.
(credit: Alain COSTA).

 

 

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