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Title: IMPORTATION AND ESTABLISHMENT OF LYGUS HESPERUS NYMPHAL PARASITOIDS IN CENTRAL CALIFORNIA

Author
item PICKETT, C
item GODFREY, K
item MAYHEW, D
item CASANAVE, K
item COUTINOT, D
item ERTLE, L
item Hoelmer, Kim

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2002
Publication Date: 8/1/2002
Citation: PICKETT, C.H., GODFREY, K., MAYHEW, D.A., CASANAVE, K., COUTINOT, D., ERTLE, L., HOELMER, K.A. IMPORTATION AND ESTABLISHMENT OF LYGUS HESPERUS NYMPHAL PARASITOIDS IN CENTRAL CALIFORNIA. NATIONAL COTTON COUNCIL BELTWIDE COTTON CONFERENCE. 2002.

Interpretive Summary: Western tarnished plant bug (lygus) is a serious pest in California of cotton, strawberries and seed crops. Native natural enemies are not very effective in suppressing lygus populations, so more effective natural enemies of lygus bugs have been imported from Europe and released in central California since 1998. Parasitoids were collected in Europe by CABI Bioscience and USDA-ARS. Two species of of braconid wasp from Spain, Italy, and France were released in California against Lygus in Sacramento test plots of alfalfa in 1998, and at several locations in central California during 1999-2001. Successful reproduction and survival over winter of the imported parasitoids was documented in spring 2000. More recoveries were made in spring 2001 at two sites. The proportion of lygusbugs attacked by the exotic wasps at the Sacramento site increased significantly from May 2000 to August 2001. Parasitoids were recovered in summer 2001 from most sites where repeated releases were made beginning in late spring/early summer. These findings suggest that the introduced lygus natural enemies are establishing in California.

Technical Abstract: Western tarnished plant bug, Lygus hesperus, is a serious pest in California of cotton, strawberries and seed crops. To establish exotic parasitoids that attack L. hesperus nymphs, parasitoids have been imported and released in central California since 1998. Parasitoids were collected from 1997-2001 in European alfalfa infested with Lygus rugulipennis by CABI Bioscience and USDA-ARS European Biological Control Laboratory. Peristenus stygicus was collected in Spain, Italy, and France, and P. digoneutis was collected in Italy and Spain. Releases in California of Lygus nymphs parasitized by P. stygicus were first made into a CDFA test plot of alfalfa in August 1998. During the summers of 1999-2001 parasitized lygus and adult P. stygicus and P. digoneutis were released at 4-7 locations in central California. In 2001, releases were made at 7 sites. CDFA maintains a Lygus colony to increase numbers of Peristenus for release. Approximately 1100, 6000, 15,000, and 14,710 parasitoids were released during summer 1998, 1999, 2000, and 2001, respectively. Parasitoids survived and reproduced following releases made in fall 1999-spring 2000 and from fall 2000-spring 2001. The first overwintering recovery of P. stygicus was made in spring 2000. It was also recovered in spring 2001 at two sites. The proportion of Lygus parasitized at the CDFA site increased from 3% in May 2000 to 34 % in August 2001. Parasitoids were recovered in summer 2001 from 6 of 7 sites where repeated releases were made beginning in late spring/early summer. All recovered parasitoids have been identified as P. stygicus.