Sharpshooters caught in biological crossfire: Non-target impacts of the glassy-winged sharpshooter egg-parasitoids in Southern California
Elizabeth A. Boyd, email@example.com and Mark S. Hoddle, firstname.lastname@example.org. University of California, Department of Entomology, Riverside, CA
In a retrospective study of the glassy-winged sharpshooter (GWSS, Homalodisca vitripennis (Germar), Hemiptera: Cicadellidae) biological control program in southern California, two egg-parasitoids, Gonatocerus ashmeadi Girault and G. fasciatus Girault (both Hymenoptera: Mymaridae), were examined for non-target effects on three indigenous sharpshooters. Rigorous host specificity tests involving choice and no-choice experiments were conducted to estimate the physiological and ecological host ranges of the parasitoids in the laboratory. Supplemental field surveys explored how closely the laboratory studies estimated invasiveness of the non-native parasitoids and their possible non-target impacts. Laboratory tests yielded no parasitization of the blue-green sharpshooter (BGSS, Graphocephala atropunctata (Signoret), Hemiptera: Cicadellidae) eggs by either of the parasitoids. G. ashmeadi did not parasitize eggs of the green sharpshooter (GSS, Draeculacephala minerva Ball, Hemiptera: Cicadellidae), but G. fasciatus did. Both G. ashmeadi and G. fasciatus parasitized the eggs of the smoke-tree sharpshooter (STSS, Homalodisca liturata Ball, Hemiptera: Cicadellidae). Field surveys confirmed infiltration of G. ashmeadi, but not G. fasciatus, into BGSS, GSS, and STSS natural environments. The habitat surveys failed to reveal non-target effects of the two parasitoids on BGSS and GSS eggs, but confirmed parasitization of STSS eggs by G. ashmeadi. The future of risk assessment in arthropod biological control is discussed.
Species 1: Hemiptera Cicadellidae Homalodiscacoagulata (glassy-winged sharpshooter) Species 2: Hymenoptera Mymaridae Gonatocerusashmeadi Species 3: Hymenoptera Mymaridae Gonatocerusfasciatus