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Phrydiuchus tau
Biological agent type
crown/root weevil.
Plant species attacked
Mediterranean sage (Salvia aethiopis)
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Phrydiuchus tau adult
Phrydiuchus tau damage
Images by Eric Coombs, Oregon Department of Agriculture.
Phrydiuchus tau larvae
If images are downloaded and used from the ODA web site please be sure to credit the photographer.
Site of attack
Leaves and root crown.
Mode of attack
The adults feed on the leaves, and the larvae feed in the root crown and in the petioles of large leaves.
Destructive stage
Adult and larval-internal.
Collection and release information
Widespread in Lake and Klamath Counties.  Agent can be collected in the adult stage May-June with a sweep net and October-November by aspirating them from rosettes.  Consult with ODA for availability for your area.
History in Oregon
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 some Lake County sites (primarily in the Goose Lake basin) that have competitive vegetation. Sites with salt desert scrub and dominated by annual grasses show little control, especially in the Abert Lake basin that have been burned by wildfires. In 1995, 26 biocontrol sites from the 1970’s and 1980’s were inventoried, of which 21 sites had mature plant densities less than 1 m2. Only 11 sites were under excellent control, < 0.01 m2. In 2005, a population outbreak of the weevils caused severe defoliation in the Abert Lake area. Biological control appears to be less effective at higher elevations in the Hart Mountain area.
Release status in Oregon
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distribution map