Agent: Crown root weevil Plant species attacked: Mediterranean sage Phrydiuchus tau Salvia aethiopis
Impact on target plant: The adults feed on the leaves, and the larvae feed in the root crown and in the petioles of large leaves. Adult feeding in the late fall and late winter can cause significant mortality of smaller rosettes.
Collection and release: Adults can be collected during the mating period by aspirating them from the rosettes in the fall; or by sweep netting emerging adults in the summer at mid-bloom. Releases should consist of 100 adults.
Distribution: The weevil has been released and established in four Oregon counties.
History: The crown/root weevil Phrydiuchus tau was released in 1972, and is widely established throughout most infestations in Lake and Klamath Counties. Successful biological control has occurred at many Lake County sites (primarily in the Goose Lake basin) that have competitive vegetation. Sites with salt desert scrub and those dominated by annual grasses show little control, especially in the Abert Lake basin that has been burned by frequent wildfires. Biological control appears to be less effective at higher elevations in the Hart Mountain area. An outbreak of Mediterranean sage occurred in the Summer Lake area following a major fire several years ago. Within four years, weevil populations naturally responded and caused extensive damage to plants.
Oregon Department of Agriculture Noxious Weed Control Program Photos by Eric Coombs, Oregon 635 Capitol Street NE Salem, OR 97301 Department of Agriculture, 503-986-4621 www.oregon.gov/ODA/programs/Weeds/Pages/Default.aspx Bugwood.org March 2016