BIOLOGY: Adult M. janthinus emerge from stems in May, and reproduce until late June. Adults are appx. 4 mm long. Eggs are laid in cavities inside the stem. Eggs hatch in 7 days. Larvae development takes 20-30 days. Larvae are 1-2 mm long, cream colored and C-shaped with brown head capsules. Pupation occurs in stems. Adults overwinter in stems.
DESTRUCTIVE STAGE: Larvae (stem mining) and adult (feeding on foliage)
IMPACT TO HOST: Impact of weevils is most effective during drought years. Control is usually 60-75%, although several sites in Utah have collapsed after 6-7 years
REDISTRIBUTION: Adults can be collected in May and June using a sweep net and aspirator or by picking insects directly 0 of plants. A typical release is 250-500 weevils. Releases should be made in dense infestations of dalmatian toadflax.
- SCIENTIFIC NAME: Mecinus janthinus
- COMMON NAME: Toadflax stem boring weevil
- TYPE OF AGENT: Insect: Beetle (Coleoptera: Curculionidae)
- GENERATIONS PER YEAR: One
- OVERWINTERING STAGE: Adult (inside pupal cell)