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 (all of the seeds of diffuse knapweed and 25–100% of spotted knapweed)[1] and the adult does damage by defoliating the plant as it feeds on the leaves prior to flowering.

[5] 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 (Diptera: Tephrididae).

[1] It is now established in knapweed populations throughout the western United States, especially in warm, dry areas.