Text Size:   A+ A- A   •   Text Only
Site Image
Subanguina picridis
Biological agent type
leaf/stem gall nematode
Plant species attacked
Russian knapweed (Acroptilon repens)
Click on image to view larger photo.
Subanguina picridis galls
Grass returning at nematode release site.
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
Stems, leaves, and root crowns.
Mode of attack
The nematodes attack the shoots as they grow up through the soil and cause galls to form on the stems and leaves. The galls look like tiny tennis balls and cause stunting of some plants and killing others.
Destructive stage
Adult and larval-internal.
Collection and release information
Limited to nursery sites at this time. Consult with ODA for availability for your area.
History in Oregon
In 1990, an experimental release of the gall nematode Subanguina picridis was made in Crook County, which failed to establish. Additional releases were made in several counties in 1993 and 1994, all were recovered, but in small numbers. In 1998, only two release sites, in Jefferson and Wheeler Counties, showed symptoms of nematode attack. The larvae can survive several years in the soil without showing any signs of attack, then cause significant impacts on plants when soil moisture is adequate. Experimental releases of nematode infested soil have been made at several other locations, but have not yet been recovered. Control appeared to be promising at Springer’s Spring in the Crooked River National Grassland, where there was 80% reduction causing a 20 foot hole in the knapweed, but the site was reinfested by September from surrounding uninfested plants.
Release status in Oregon
Click on map to view larger image.
distribution map