|Biological agent type
knapweed root borring moth.
Plant species attacked
diffuse knapweed (Centaurea diffusa)
spotted knapweed (Centaurea stoebe)
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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
Cortex and cambium of the root.
Mode of attack
The larvae girdle and bore into the roots, causing severe damage.
Larval-internal and larval-external.
Collection and release information
Limited in distribution at this time. Adults are collected during June and July at night with the use of light traps.Consult with ODA for availability for your area.
History in Oregon
In 1987, the root-boring moth Agapeta zoegana was released near Hood River. The moth is well established in several counties and is collectible in Hood River and Enterprise. This insect is also known to attack diffuse knapweed. Several larvae may occur together in the same plant. At release sites where Sphenoptera jugoslavica also occurs, the number of Agapeta larvae decreased by more than 80%.
Release status in Oregon
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