Native parasitoids associated with the biological control agents of Centaurea stoebe in Montana, USA Herron-Sweet et al. 2015
The long-term vulnerability of biocontrol agents to parasitism by native organisms is a concern for the practice of classical biological control, especially for agents that have been established for several decades. A recent study by Montana State University identified parasitoids attacking spotted knapweed biocontrol agents in Montana and determined the percent parasitism of any host-parasitoid associations found. Nine species of parasitoid emerged, four of which were previously unknown associations with these biocontrol agents. Parasitism rates of the seed head gall fly (Urophora affinis) were surprisingly high, reaching 100% in some cases.