|Cabrera-la Rosa, Juan|
Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/26/2007
Publication Date: 8/1/2007
Citation: Fritschi, F., Cabrera-La Rosa, J.C., Groves, R.L., Lin, H., Johnson, M.W. 2007. Behavioral Responses of Homalodisca vitripennis (Hemiptera: Auchenorrhyncha: Cicadellidae) on Four Vitis Genotypes. Environmental Entomology. Vol. 36, Issue 4, pp. 926-936. Interpretive Summary: Pierce’s Disease is a major threat to the California grape industry. The disease is caused by a bacterium that is spread by insect vectors including the glassy-winged sharpshooter (GWSS). Spread of the pathogen is influenced by behavior of the insect vector. It is well known that many insects exhibit selective behavior towards potential plant hosts. In this study we investigated adult GWSS responses to four types of grape (Vitis vinifera (‘Chardonnay’), V. girdiana, V. candicans, and a V. rupestris x V. arizonica hybrid: D8909-17). It was clear that, under controlled environmental conditions, GWSS preferred some grape cultivars over others. The selection of a host grape type was also affected by the grape type the insects were acclimated on prior to giving them a choice. In addition, GWSS mortality was influenced by the type of grapes. In this study, the type of grape was shown to influence behavior of the GWSS. These experiments provide early information for future research to identify ways in which GWSS behavioral traits may be explored to minimize the spread of Pierce’s disease.
Technical Abstract: Pierce’s Disease is a major threat to the California grape industry. The disease-causing bacterium Xylella fastidiosa is vectored by a number of leafhoppers including Homalodisca coagulata (Say) (Hemiptera: Cicadellidae). Experiments were conducted to investigate H. coagulata preference, feeding, and survivorship in response to four Vitis genotypes. Plants of V. vinifera (‘Chardonnay’), V. girdiana, V. candicans, and a V. rupestris x V. arizonica hybrid (D8909-17) were grown in pots in the greenhouse and transferred to laboratory conditions for experiments with field-collected H. coagulata. A choice test without prior insect acclimation on grapes revealed that H. coagulata selected Chardonnay over V. candicans throughout the duration of the experiment while a shift in preference between 8909-17 and V. girdiana was observed over time. In a second set of choice tests, which were preceded by an acclimation on one of the four grape genotypes, significant genotype, time and acclimation x genotype effects were observed. Chardonnay was preferred over V. candicans independent of acclimation genotype. While H. coagulata confined on 8909-17 excreted 1.8-fold (dry-weight corrected) the amount of insects feeding on V. candicans, differences in the rate of excreta production per insect or insect dry weight were not significant among grape genotype. Adult mortality was greatest on V. candicans when H. coagulata were confined in parafilm sachets for excreta collection as well as in a no-choice test. Grape genotype affected the behavior of adult H. coagulata under controlled conditions, which may influence Pierce’s Disease epidemiology under field conditions.