Annu.Rev. Entomol.1993.38:27-51 MANAGEMENT OF GENETICS OF BIOLOGICAL-CONTROL INTRODUCTIONS 1 K. R. Hopper European Biological Control Laboratory, Agricultural Research Service, United States Department of Agriculture, BP4168, 34092 Montpellier,France R. T. Roush Department of Entomology, Comstock Hall, Comell University, Ithaca, New York 14853 W. Powell AFRC Farmland Ecology Group, Entomology and Nematology Department, Rothamsted Experimental Station, Harpenden, Hefts AL5 2JQ, United Kingdom KEY WORDS: genetic variation, host specificity, laboratory rearing, adaptation, parasitoids PERSPECTIVES AND OVERVIEW For over 100 years, arthropod pests and weedshave been controlled by the introducion of exotic natural enemies (21). For almost as long, entomologists have discussed the importance of genetics and the possibility of genetic manipulations in biological control, and today these remain subjects of considerable debate. Perhaps the first issue raised was that predators and parasites mightbe artificially selected for improved performance in the field (46, 47, 59). In contrast, a major concernfor laboratory rearing of insects and mites used in biological control is that such rearing will promote genetic adaptation to laboratory conditions and thus worsenperformance in the field (57, 58). Anotherconcern is that natural enemies imported for biological control constitute only a limited sample of the genetic variation present in the species, and may therefore lack the ability to adapt to their new environment (64, 65). Many of these issues, and possible solutions, have been discussed recently 1The U.S. Government has the right to retain a nonexclusive royalty-free license in and to any copyright covering this paper. 27 Annual Reviews www.annualreviews.org/aronline