Tephritis arnicae

The fly of the arnica , ( Tephritis arnicae ) is a Diptère of the family Tephritidae and kind Tephritis . Except for some rare exeptions, it is completely pledged with the plant host of its larva: Arnica Montana which develops in the acid mountains European. Its ratéfiant himself host, it follows this evolution logically. Major medicinal plant of the European Pharmacopeia S, the arnica is the subject of many experiments of cultures, Tephritis arnicae became one of its ravageurs about it.

Description

the Imago S , small flies with the wings mottled of brown, fly as of May/June, their coupling and the laying of the females succeeding their first appearance quickly. the egg S , spindle-shaped, white and long 0,6 mm are deposited by small packages (from 2 to 4) on or between the tubular flowers in formation, inside the little developed floral buttons Arnica Montana . The presence of larvae of different ages testifies that one or more females can deposit their laying there successively.

the larval development includes/understands three stages from 20 to 40 days, from end-June to the beginning of August. The larvae Apodal S, initially spindle-shaped, quickly take the aspect of a white maggot creams and clearly segment. They nourissent tubular flowers, and more particularly of the ovary S, than they perforate, even penetrate of the totality of their body, the head directed downwards. So of many larvae divide the same flowerhead (up to 15, they devour the receptacle, then invade sometimes the first centimetres of the stem. Mature, they reach 4 to 5 mm length.

the Nymphose , one 20 days intermediate duration, is held within the puparium in the shape of small small cask sinks (of brown dark with black) and cover from where the Imago will emerge. Thus, the totality of the development pre imaginal occurs within the flowerhead which filled a double function, that of pantries and that of physical protection against the possible predatory ones or parasitoïdes. Indeed, two species of hymènoptères seem to parasitize the larvae of Tephritis arnicae: Pteromalus alpipennis Walker and Pronotolia carlinarum Szelényi & Erdoes

From July to August, takes place spread out emergence of the Imago S . After their dispersion, these adults leave their plant host during the cold season for to winter as of the autumn in more lenient areas and on other plants. The appearance to of consequent number of Tephritis arnicae on cultures flowering for the first time testifies to the great aptitude of migration of the insect in order to discover new stations plant-host. Moreover, that suggests that T. arnicae does not train stable and pledged populations with a precise site but which it colonizes each year an unspecified zone, starting from its place of hivernation. The colonization of these new sites is carried out whereas the plant approximately forms only a rivet washer 5 cm in diameter. By consequence, volatile substances emitted by the sheets (of aillor very charged in essential oils) could intervene in this gravitational phenomenon. As for the parades, the presence of male on the rivet washers at any beginning of spring seems to testify to the meeting to the partners and fecundation on the station itself.

Ecology and distribution

Synchronization of Tephritis arnicae with Arnica Montana

The periods of flight of the adults coincide with the flowering of the arnica. Their dates thus fluctuate according to the altitude and of the latitude of the site, according to the precocity and the speed of development of the arnica. This perfect sychronisation between the ravageur and its host results from a long process of coévolution, phenomenon frequent at the Tephritidae , as much on the morphological level that in the development cycle. At Tephritis will conura , a species close infesting the flowers to Cirsium heterophyllum , Roemstoeck-Voelkl (1990) clearly highlighted the influence of the synchronization of the period of deposit of eggs in the floral buttons (oviposition) with the stage phenologic of the plant on the degree of infestation of a given site. In addition, the number of adults present on a site is closely related to the number of buttons offering of the favorable conditions to the plant. By analogy, the females of T. arnicae would be " prêtes" to lay at the same time as the appearance of the first buttons.

A ravageur of the cultures of Arnica Montana

See also: Arnica Montana

From the flowerheads of the arnica, one extracts an officially recognized drug, in order to look after the Inflammation S and the Ecchymose S. Although these larvae are easily extracted and that the flowerheads parasitized are usable after cleaning, certain authors say it very toxic while others show this larva to make lose with the Arnica its medicinal properties. Present on the wild stations, it is not less Ravageur on the cultures. Considering, the economic damage of dipterous, the federal Station of agronomic research of Changins (Swiss) at summer elected by Weleda in order to dam up the problem of its test culture. Their study proposes adapted means of fight.

The colonization of new sites of arnica taking place as of the first harvest year, it is appropriate to protect the culture as of the year from installation.

the Larva S being well protected from the Predatory S and the Parasitoïde S, but also from chemical substances by the Bractée S of the floral buttons, a fight by released of antagonist and Insecticide S natural (Roténone) is excluded. Employs penetrating synthetic substances is to be excluded for toxicological reasons.
employs It traps with Mouche of the carrot seems ineffective when with the fall of the rate of infestation.
the crop protection by a net anti-insect seems to be most effective on the one hand because its effectiveness can border the 100% and on the other hand because it does not present the disadvantages of a use in Plaine caused by strong a thermal rise under the net. The date of installation should be posed at the latest fifteen days after the appearance of the rivet washers (made abstraction of the weather conditions) and will have to remain in place until the lifting of the floral poles (10-15 cm in height). However, this will have to answer a compromise between the fight against the ravageur and the farming requirements (Sarclage, weeding) Moreover, the presence of net influences the development of cryptogamic diseases, in particular cemlles of the coal of the arnica ( Entyloma arnicalis ) the plants reached see their development strongly blocked before and/or after their flowering. It appears that a genetic selection of resistant stocks would make it possible to dam up the problem.

Sources

Reference SITI: Tephritis arnicae L.
Reference The Diptera Site: The BioSystematic Database off World Diptera
Biology of Tephritis arnicae L. (Diptera, Tephritidae) and fights against this ravageur of the cultures of Arnica Montana L. Emery S; Delabays NR; Fischer S; Federal station of agronomic research of Changins (Swiss) Swiss Review Vitic Arboric Hortic; 27 (5) Page (S) 301 - 307 (1995)
Manfred Pfeifer: Phytophagous Insekten year ausgewählten Compositen (Asteraceae) in einem inneralpinen Gebiet (Paznauntal, Nordtirol, Österreich) : Tephritis arnicae year Arnica Montana

External bonds

Photographs of Pupes and wings of Tephritis arnicae

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