OVIPOSITION AND NATIVE PARASITOIDS OF THE BLUE-GREEN SHARPSHOOTER, AND HOST SPECIFICITY OF GONATOCERUS ASHMEADI ON THE SMOKETREE SHARPSHOOTER AND THE BLUE-GREEN SHARPSHOOTER

• Author(s): Hoddle, Mark; Boyd, Elizabeth;
• Abstract: The studies outlined below represent two years of a three year project. We have determined the oviposition preferences of Graphocephala atropunctata (Signoret) (Hemiptera: Cicadellidae), blue-green sharpshooter, (BGSS) on wild grape, have documented its associated egg parasitoids, and provide data on host specificity of Gonatocerus ashmeadi, a parasitoid being used as part of the classical biological control program against glassy-winged sharpshooter (GWSS), Homalodisca coagulata Say (Hemiptera: Cicadellidae) on the targets congener, the native Homalodisca liturata Ball, smoketree sharpshooter (STSS), as well as the BGSS. To determine the oviposition of female BGSS, a survey was conducted on southern California wild grape, Vitis girdiana Munson (Vitaceae) growing near Temecula, CA in August 2003 and 2004 where populations of BGSS were known to occur. Female BGSS oviposited into new growth, primarily the succulent tendrils and stems. Two parasitoids, Gonatocerus latipennis Girault and a Polynema sp. (Hymenoptera: Mymaridae) were reared from BGSS eggs. Deployment of sentinel plants and reciprocal tests were implemented to further confirm the parasitization of BGSS eggs by these parasitoids. Collectively the Polynema sp. and Gonatocerus latipennis constitute the first documented natural enemies of BGSS eggs. Additional studies, commencing in January 2004, of the activity of BGSS and its parasitoids in southern California is currently underway. Blue-green sharpshooter adult activity reached its peak in July while bi-weekly samples of wild grape canes and tendrils revealed peak emergence of BGSS nymphs and parasitoids occurred from mid-July to mid-August. These peaks were found to be significantly correlated. Choice and no-choice tests of Gonatocerus ashmeadi Girault and G. fasciatus, (Hymenoptera: Mymaridae) parasitoids of GWSS with the native smoketree sharpshooter (STSS), and BGSS eggs as part of a retrospective non-target impact assessment have yielded interesting results. Parasitism of STSS eggs by G. ashmeadi and G. fasciatus does not appear to be significantly different when compared to the GWSS control in no-choice experiments. Additionally, it appears G. ashmeadi exercises no preference of host eggs for parasitization when presented with a choice of STSS and GWSS simultaneously.
• Publication Date: Dec 2005
• Journal: 2005 Pierce's Disease Research Symposium