Status ofCoccobiusnr.Fulvus(Hymenoptera: Aphelinidae), a Parasitoid of Euonymus Scale (Hemiptera: Diaspididae), 12–16 Years After Its Release in Massachusetts

Abstract

From 1990 to 1995, a classical biocontrol pro gram was conducted in New England against an Asian scale, Unaspis euonymi (Comstock) (Hemi ptera: Diaspididae), which attacks landscape Eu onymus plants. Many Euonymus species are of Asian origin (Flint 1983) and widely planted as ornamentals (Gill et al. 1982). Collection of eu onymus scale natural enemies for release in the USA began in Korea (Drea & Hendrickson 1988; Hendrickson et al. 1991), but from 1990-1995 our laboratory collected additional species near Beijing, China (Van Driesche et al. 1998a), includ ing 2 predators (Chilocorus kuwanae Silvestri and Cybocephalus nr. nipponicus Endrody Younga) and 3 parasitoids (Coccobius nr. fulvus (Compere et Annecke), Encarsia nr. diaspidicola (Silvestri) and Aphytis sp.). Impacts of the 2 pred ators have been documented (Van Driesche et al. 1998b; Van Driesche & Nunn 2003). In 1991-1994, 3,862 adult C. nr. fulvus were re leased at 11 sites; 12,966 adults, nr. diaspidicola at 27 sites; and 801 adult Aphytis sp. at 5 sites in New England (mostly Massachusetts) (Van Drie sche et al. 1998a). By 1994, apparent establish ment (recovery in 1 subsequent year following re lease) had occurred for C. nr. fulvus and E. nr. di aspidicola. No next-year recoveries were made for Aphytis sp., the species released last and in small est numbers. No evidence of spread of any parasi toid was observed. In addition, a pre-existing cos mopolitan polyphagous aphelinid, Encarsia cit rina (Crawford), was observed in samples from Massachusetts. In 1991, it was detected at 44% of 79 sites in southern New England. In 1994, para sitism of dissected adult female euonymus scales by E. citrina, pooled by generation across 18 loca tions in Massachusetts, averaged 13.4% (n 2,174 scales) for the overwintered spring adults, 33.6% (n = 1,271 scales) for the summer generation, and 31.2% (n = 933 scales) for the fall generation. Our objectives here were (1) to sample for ex otic parasitoids of euonymus scale in western Massachusetts in 2006 and 2007 at their original release sites, (2) to sample non-release locations to detect parasitoid spread, and (3) to assess ef fects of exotic parasitoids on the pre-existing par asitoid E. citrina.