APPROVED BIOLOGICAL CONTROL AGENTS
Phrydiuchus tau, or the Mediterranean sage root weevils, are characterized by the prominent white “T” on their backs. Adults emerge in late spring or early summer. After feeding on the foliage, they rest in summer aestivation until fall rains arrive and the plant begins to grow again.
Adult females lay eggs in the leaf axils, petioles, and on the undersides of rosette leaves. Eggs hatch 24 to 28 days after oviposition. Larvae tunnel through the leaves into the root crown, where larval development occurs.Mature larvae pupate in the surrounding soil from early May to July. Larval feeding in the root crown damages plants thereby reducing or preventing bolting, and in some cases kills the plant. Adults may impact the plant too, causing minor defoliation of rosette leaves.
Collections should be done in late spring or early summer using a sweep net or knocking them into a container. This agent does best at warm, dry sites and does not seem to establish at wetter sites and/or sites that receive snow before mid-November.
Approved Biological Control Agents for release in Idaho: