Cyphocleonus achates
Biology
C. achates adults emerge from June to September. They are large (14-15mm long) and live for 2-3 weeks. Females lay one egg at a time in the root crown just below the soil. A female will mate and lay eggs over 100 times. Larvae undergo 4 instars. The fourth instar overwinters and pupates in June.
Destructive Stage
Larvae (root feeding and root galling)
Impact To Host
First and second instar larvae reduce root mass. Third and fourth instar larvae form swelling and galls in roots. C. achates can kill knapweed plants in a single year, but populations are often not dense enough to reduce entire stands of knapweed. C. achates will be most effective when released with other knapweed biological control agents.
Redistribution
Adults can be collected by picking them directly off of plants in the middle of the day in July. A release is typically 50-75 C. achates.
