BIOLOGY: Adults emerge from soil in late May and are present through August. They are hairy and brown with white stripes. Adults are 4-6mm long. Eggs are laid in early to mid-summer. Females bore a hole into the seed head and deposit eggs. Eggs hatch in 3 days. Larvae feed on the seed head until larval development is complete (appx. 16 days). Pupation occurs in the seed head and lasts 8-13 days.
DESTRUCTIVE STAGE: Larvae and adult (seed head feeding)
IMPACT TO HOST: Larvae destroy seed heads. Adults feed on mature buds. Larvae can reduce seed production as much as 90-100% and reduce an infestation of yellow starthistle in 5 years.
REDISTRIBUTION: Adults can be collected in late June and early July using sweep nets or by picking adults off of plants. A typical release is 250 adults. E. villosus can be released on any size infestation from several meters to several miles.
- SCIENTIFIC NAME: Eustenopus villosus
- COMMON NAME: Yellow starthistle hairy weevil
- TYPE OF AGENT: Insect: Beetle (Coleoptera: Curculionidae)
- GENERATIONS PER YEAR: One
- OVERWINTERING STAGE: Adult (in soil)