Glassywinged Sharpshooter [Homalodisca coagulata (Say)]

An immigrant mymarid parasitic wasp, Gonatocerus ashmeadi Girault, played a major role in the suppression of the population of the glassywinged sharpshooter (GWSS) in Hawaii. In all likelihood, G. ashmeadi arrived in Hawaii in association within parasitized GWSS eggs on infested host plants that were shipped from the southern United States, most probably California or Florida. The presence of the parasitoid was not apparent when the pest was first detected in early 2004. Heavy infestations were observed on a wide variety of plants and an average of six dispersing adults was consistently caught per yellow sticky card until November 2004. However, beginning in December 2004, the trap counts began to decline to fewer than half as many adults caught per trap. 

The dramatic decline in GWSS densities continued throughout much of 2005 and, by June 2006, no GWSS was trapped.  Concurrent to the rapid decline of GWSS, the very first evidence indicating the presence of G. ashmeadi in Hawaii was recorded in November 2004. Although GWSS parasitization was initially low (20 percent), by April 2005, the rates of parasitization had exceeded 90 percent. Periodic monitoring of GWSS eggs from at least seven locations indicated that 96 percent of 3,383 total eggs sampled from July to November 2005 were heavily parasitized. Subsequently, no parasitization data were generated because no GWSS eggs could be detected in the host habitat.  

GPS surveillance, visual inspection of host plants, and egg sampling showed that the GWSS distribution was limited to the leeward side of Oahu. In addition to previously recorded hosts, tropical almond, Terminalia sp. (Family Combretaceae) and Erythrina variegata (Family Fabaceae) were also found to be infested by the GWSS. Although a small infestation was detected at Heeia in Kaneohe, continuous monitoring of the area indicated that the pest had not spread to other locations in Windward Oahu. Moreover, surveys conducted in February and March 2006 on Kauai and Maui showed that the GWSS had not yet dispersed to those islands.