|Biological agent type
seed head fly
Plant species attacked
spotted knapweed (Centaurea stoebe)
diffuse knapweed (Centaurea diffusa)
Click on image to view larger photo.
Images by Eric Coombs, Oregon Department of Agriculture.
If images are downloaded and used from the ODA web site please be sure to credit the photographer.
Site of attack
Mode of attack
Larvae tunnel through the seed head destroying seeds.
Collection and release information
This bio-agent is limited in numbers in Oregon. Consult with ODA for availability for your area.
History in Oregon
The seed head fly Chaetorellia acrolophi was first released in small numbers in Hood River, Lane, and Deschutes Counties in 1993. In 1994, they were released a second time in Hood River and Deschutes Counties. The fly is becoming more abundant in the Hood River area and below Cougar Reservoir in Lane County. It also known to attack diffuse knapweed.
Release status in Oregon
Click on map to view larger image.