Submitted to: Biocontrol Science and Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/23/2006
Publication Date: 2/20/2007
Citation: Pickett, C.H., Rodrigeuz, R., Coutinot, D., Hoelmer, K.A., Kuhlmann, U., Goulet, H., Schwartz, M. 2007. Establishment of Peristenus spp. (Hymenoptera: Braconidae) in California for the control of Lygus spp.. Biocontrol Science and Technology. v. 17, issue 3, pp 261-272. Interpretive Summary: Tarnished plant bugs (lygus bugs) are serious pests of many different crops throughout North America. They are typically managed with applications of broad spectrum insecticides. Extensive surveys for native natural enemies of tarnished plant bugs in the western U.S. found only very low levels of natural enemy impact. Importations of exotic biocontrol agents during previous decades were conducted but they did not become established. However, successful establishment of imported biological control agents in the eastern U.S. during the 1980’s has resulted in lower tarnished plant bug populations infesting alfalfa in the northeastern U.S. Renewed efforts were recently made to introduce populations of European natural enemies specifically from climatic regions closely resembling that of California. These introductions appear to have successfully colonized several locations in central California.
Technical Abstract: Lygus hesperus is native to western United States and is a perennial pest of numerous crops in California. It is responsible for triggering early season applications of insecticides on cotton and strawberries. Surveys of Lygus in alfalfa grown in central California have never shown significant levels of parasitism by native nymphal parasitoids associated with this pest. Two exotic braconid nymphal parasitoids of Lygus were imported into California beginning in 1998. Peristenus stygicus and P. digoneutis were collected from several locations in southern Europe, cleared through quarantine and shipped to California. Peristenus spp. were released at up to five locations over a 6 year period. At the original release site in Sacramento, a 0.25 ha plot of alfalfa, both P. digoneutis and P. stygicus have continued to increase in numbers through 2004, 3 years after last releases were made. Parasitism has reached a high of 90%, and numbers of Lygus at this location have begun to decrease. Parasitoids have also been recovered from vacant fields of weedy annuals within 2 km of this site. Recoveries at more southerly release sites in central California have been poor.