The garlic fly is one of the most important pests in garlic cultivation in the East of Austria. This pest only infests winter garlic, not summer garlic, which is seeded in spring. Moreover, some types of garlic are more susceptible than others: the traditional, local type of garlic grown in the Weinviertel region appears to be less infested or, at least, more resistant to infestation.
Biology
The flies have red-brown bodies, a wingspan of about 18 mm with mostly translucent wings and a grey shine along the wing veins. Like all flies, they possess halters, dumb-bell shaped organs, instead of hindwings. The flies winter as adults.
Bild: Adult garlic flies are 14 mm long and brown-red in colour. Their wings show a dark shadow along their horizontal veins.
In early spring, just after the melting of the snow and as soon as the first garlic shoots emerge from the ground, the flies migrate to the garlic fields and deposit a white, ca. 1.2 mm long, spindle-shaped egg with a strongly sculptured surface in the soil near the base of the stem. The peak of egg deposition is in the first half of April.
The larvae bore into the shoots and start to feed on the young leaves as soon as they have hatched from their eggs. The feeding marks will only become visible once the affected leaves are pushed to the outside during growing. The maggot’s frontal end is pointed with the mandibles shining through as little hooks, while their strongly sclerotized spiracles (stigmata) end in the posterior.
The larvae go through three stages before the maggots reach their final size of about 10 mm. They leave the garlic plant around mid-May and pupate in the surrounding soil. The oval, dark brown puparium is around 7 mm long. From this puparium, the new flies emerge at the beginning of June. The adult flies do not cause any more damage, they overwinter and reproduce next spring.
AGES - Austrian Agency for Health and Food Safety
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