Population ecology of Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae) and host selection behavior of associated egg parasitoids.

摘要

Various aspects of the biology and behavior of glassy-winged sharpshooter (GWSS), H. vitripennis, and its natural enemies were studied. A study was conducted in a citrus orchard to determine the influence of plant water stress on the population dynamics of GWSS. Experimental treatments included irrigation at 100% of the crop evapotranspiration (ETc) and deficit-irrigation regimes at 80% and 60% ETc. GWSS populations were monitored weekly by visual inspections, beat net sampling, and trapping. GWSS populations were negatively affected by severe plant water stress. Citrus trees irrigated at 60% ETc had warmer leaves, higher xylem matrix potential, and smaller numbers of GWSS eggs, nymphs, and adults than trees irrigated at 80% ET c. Gonatocerus ashmeadi Girault is an egg parasitoid of GWSS in California. I tested the hypotheses that G. ashmeadi uses chemical volatiles as cues in host finding and the wasp's host finding success varies among plant species. Citrus, grapevine, red tip photinia, and crape myrtle plants were offered to parasitoids using a glass Y-tube olfactometer to determine parasitoid preferences for volatiles of GWSS-infested versus uninfested plants. The parasitoid's first choice, residence time, and number of visits per Y-tube arm were recorded. Females initially chose, spent more time within, and made more visits to the Y-tube arm connected to the plant with GWSS eggs and feeding injury versus the control plant, except for crape myrtle. Anagrus epos Girault is a candidate for a classical biological control program targeting the GWSS. In choice and no-choice tests for oviposition, A. epos parasitized all GWSS egg ages (1 to 8 days old), but parasitism rates were higher in younger eggs (1 to 5 days old). If provided with honey and water versus no food or water, A. epos females lived on average 8.2 and 1.6 days, respectively. Anagrus epos required 294.1 degree-days, above a lower temperature threshold of 12.4°C, to develop from egg to adult (eclosion). Production of GWSS is expensive and labor intensive. Thus, factitious hosts were desirable to mass produce A. epos for augmentation efforts. Anagrus epos completed development in the eggs of seven cicadellid species: H. vitripennis, Circulifer tenellus (Baker), Erythroneura variabilis Beamer, Amblysellus grex (Oman), Graphocephala atropunctata (Signoret), Macrosteles severini Hamilton, and Homalodisca liturata Ball.