Rhagoletis complana

Walnut husk fly

Description

Walnut husk fly is native to North America and invaded Western Europe in the late 1980s, causing important damage to its principal host, walnut. It has only one generation per year. Adults fly from July to August, females lay eggs on green nuts and larvae develop in the husk of nuts. Larvae hatch in 3 to 7 days, usually living for 3 to 5 weeks. They feed on the walnut peel. Mature larvae leave the husks to pupate in the soil, where they overwinter in the pupa stage. Adults hatch in summer and the cycle is repeated. Flies are able to fly for long distances (several tens to hundreds of kilometers) - the wind helps them to spread.

Symptom

Larvae feeding in the husk tissues, can cause shell sclerotisation, darkening and molding of kernels. High infestations cause premature nut fall. Damage caused by insects attacking husks can expose susceptible tissues to colonization by toxigenic fungi . Fungi can grow on walnuts under favourable conditions and it could increase the concentration of toxins in infested walnuts.

Tree Species: Walnut

Part of a plant- attacked: Fruit / Seed

Pest significance: Very harmful

Pest Category: Insects

Invasive Species: Yes

Present in EU: Yes

Seasonal frequency of occurrence