Classical arthropod biological control programs lack a universally adopted risk assessment testing strategy for precisely estimating physiological and ecological host range of potential biological control agents. Several strategies have been proposed, yet few have been implemented and subsequently evaluated in terms of efficacy at estimating realized risk. A rigorous host specificity testing protocol was evaluated for estimating potential physiological and ecological risk to non-target species posed by exotic parasitoids introduced for use in the exotic glassy-winged sharpshooter (GWSS), Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae) classical biological control program in southern California (SoCal), U.S.A. This testing strategy was assessed at two environmental scales, with choice and no-choice host options presented on multiple plant species to egg parasitoid congeners, the solitary Gonatocerus ashmeadi Girault and gregarious G. fasciatus Girault (Hymenoptera: Mymaridae). For both parasitoids, physiological and ecological host ranges were estimated using three non-target indigenous sharpshooters, smoke-tree sharpshooter (STSS), Homalodisca liturata Ball, blue-green sharpshooter (BGSS), Graphocephala atropunctata (Signoret), and green sharpshooter (GSS), Draeculacephala minerva Ball (Hemiptera: Cicadellidae). Host specificity testing results were further evaluated by comparing observed laboratory and field non-target impacts. Results of laboratory choice and no-choice tests in both environmental scales with G. ashmeadi revealed STSS eggs were a physiologically and ecologically acceptable host, but BGSS and GSS eggs on the different plant species were not acceptable hosts. Choice and no-choice tests with G. fasciatus revealed both STSS and GSS, but not BGSS, eggs were a physiologically acceptable host. However, only STSS eggs were determined to be an ecologically acceptable host for G. fasciatus. Non-target parasitism of STSS eggs by G. ashmeadi in non-desert habitats of SoCal was determined. Field surveys failed to reveal parasitism of BGSS or GSS eggs, in their respective native habitats, by either G. ashmeadi or G. fasciatus in SoCal. Through the course of this work, a novel testing cage was designed for standardizing biological studies on arthropods, native natural enemies of BGSS and GSS were documented, oviposition preferences and SoCal day degree model were created for BGSS, and acoustic signals of GWSS, STSS, and BGSS were observed and recorded.
|Advisor:||Hoddle, Mark S., Stouthamer, Richard|
|School:||University of California, Riverside|
|School Location:||United States -- California|
|Source:||DAI-B 68/07, Dissertation Abstracts International|
|Keywords:||Biological control, Egg parasitoids, Homalodisca vitripennis, Host specificity, Mymaridae, Sharpshooters|
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