BIOLOGY: Adults are active from May to September. They are 4 to 5 mm long. Females produce 30-130 eggs in their lifetime. Up to 5 eggs are deposited in the flower head of each knapweed plant. Larvae hatch in 3 days and then spend 4 weeks in the seed head before pupating. Pupation takes 1 week. Adults drop off of plants in September and overwinter in the soil.
DESTRUCTIVE STAGE: Larvae (feeding on seed head) and adult (leaf and seed feeding)
IMPACT TO HOST: Damage can reduce stands density and provide excellent control. L. minutus will be most effective when released with other knapweed biological control agents listed in this field guide.
REDISTRIBUTION: Adult L. minutus can be collected using a sweep net or by picking them off of plants in June and July. A typical release is 150-250 adult insects.
SPECIES OF KNAPWEED ATTACKED: Diffuse knapweed, spotted knapweed, squarrose knapweed.
- SCIENTIFIC NAME: Larinus minutus
- COMMON NAME: Lesser knapweed flower weevil
- TYPE OF AGENT: Insect: Beetle (Coleoptera: Curculionidae)
- GENERATIONS PER YEAR: One
- OVERWINTERING STAGE: Adult (in soil)