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Yellow starthistle hairy weevil

Eustenopus villosus

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)
Eustenopus villosus
Eustenopus villosus
Eustenopus villosus

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Utah Biological Control

Amber Mendenhall

phone: 435 830 4146

email: utahsbuggirl@gmail.com

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contact your local County Weed Supervisor

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