Biological agent type
root boring weevil
Plant species attacked
spotted knapweed (Centaurea stoebe)
diffuse knapweed (Centaurea diffusa)
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Images by Eric Coombs, Oregon Department of Agriculture.
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If images are downloaded and used from the ODA web site please be sure to credit the photographer.
Site of attack
root and leaf
Mode of attack
The larvae are root borers and adults feed on the leaves.
Destructive stage
Larva-internal
Collection and release information
Adults can be collected by sweep net or picked by hand August-September. Limited in distribution at this time consult ODA for availability for your area.
History in Oregon
The root weevil Cyphocleonus achates was first released near Hood River in 1993. Several additional releases of the weevil were made in other counties during 1994. Adults were recovered in 1995 in Bend and they appear to be spreading throughout the area. Redistribution began in 1997. The weevil does best at sites with sparse vegetation. This weevil also attacks diffuse knapweed.
Release status in Oregon
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