Van Driesche et al.: Euonymus Scale Natural Enemies 1 RELEASE, ESTABLISHMENT AND SPREAD OF ASIAN NATURAL ENEMIES OF EUONYMUS SCALE (HOMOPTERA: DIASPIDIDAE) IN NEW ENGLAND

Between 1990 and 1995, the USDA/APHIS National Biological Control Laboratory in Niles, MI, Texas A&M University, and the University of Massachusetts conducted a biological control introduction program against the Asian diaspidid scale insect Unaspis euonymi (Comstock), a pest of woody landscape plants. Two species of predators ( Chilocorus kuwanae Silvestri, Coleop.: Coccinellidae and Cybocephalus sp. nr. nipponicus Enrody-Younga, Coleop.: Cybocephalidae) and three aphelinid parasitoids ( Encarsia sp. nr. diaspidicola [Silvestri], Coccobius sp. nr. fulvus [Compere et Annecke], and Aphytis sp.) were collected near Beijing, China and released in southern New England. We report establishment of C. kuwanae , C. sp. nr. nipponicus and Coccobius sp. nr. fulvus in Massachusetts. Chilocorus kuwanae has spread throughout southern New England and the proportion of euonymus shrubs in landscape-level surveys bearing C. kuwanae stages was positively related to scale density, with the coccinellid present on 1.1%, 6.3%, 12.5%, and 26.3% of shrubs whose scale populations were classified as none, light, medium, and heavy, among 4843 plants examined from 1992-1994 in Massachusetts, Connecticut, and Rhode Island. Cybocephalus sp. nr. nipponicus and C. sp. nr. fulvus , while established at some release sites, have been observed to spread to new locations in only one and two instances, respectively. Encarsia sp. nr. diaspidicola was recovered at some release locations, but establishment is uncertain. No recoveries were made of the Aphytis sp. parasitoid, but this species was released later than the other species and further recovery efforts are needed.