Lesser knapweed flower weevil

Appearance

The adult weevil is dark mottled brown with a long snout. It is 4 or 5 millimetres long in total. It is active throughout the summer with a 14-week maximum adult lifespan. During this time the female lays up to 130 eggs, depositing them in the knapweed flower head. The larva emerges and burrows into the flower head where it feeds on the developing seeds. The larva damages the plant by reducing seed production and the adult does damage by defoliating the plant as it feeds on the leaves prior to flowering. After flowering, adult weevils switch to feeding on flowers.

Distribution

This weevil is native to southern Europe and the Mediterranean. It was first released as a knapweed biocontrol in the United States in 1991 from Greece. It is now established in knapweed populations throughout the western United States, especially in warm, dry areas. It feeds on knapweeds, preferring diffuse knapweed over others, and it has not been shown to attack native flora. This weevil has been shown to reduce diffuse knapweed density at several sites. It has been less successful in controlling spotted knapweed.

Food

In spotted and diffuse knapweed, ''L. minutus'' directly consumes another biological control agent released to control the species, the gall-forming flies ''Urophora affinis'' Frfld and ''Urophora quadrifasciata'' Meigen