J.M. DiTomaso, The Regents of the University of California

J.M. DiTomaso, The Regents of the University of California

meadow knapweed

APPROVED BIOLOGICAL CONTROL AGENTS


Larinus minutus, L. obtusus

Larinus spp., or the knapweed flower weevils, are abundant biological control agents that can utilize spotted, diffuse, and squarrose knapweeds. These insects overwinter as adults, and emerge in the spring when they begin to feed on knapweed foliage.

Females produce between 28 and 130 eggs which they lay in clusters in open flowers. The hatching larvae feed on seeds and receptacle tissues and later construct cocoons within the seedheads using pappus hairs.

After four weeks, pupation occurs within this cocoon. Emerging adults chew a characteristic round hole in the top of the cocoon that is visible when viewed from above.