Monday, December 11, 2006

Survival of glassy-winged sharpshooter, Homalodisca coagulata (Say) (Homoptera: Cicadellidae) in relation to temperature and feeding

Youngsoo Son, youngsoo@uckac.edu1, Marshall W. Johnson, mjohnson@uckac.edu2, Russell Groves, rgroves@fresno.ars.usda.gov3, Elaine Backus, ebackus@fresno.ars.usda.gov3, and Kent M. Daane, daane@uckac.edu4. (1) University of California - Riverside, Department of Entomology, UC Kearney Agricultural Center, 9240 S. Riverbend Ave, Parlier, CA, (2) University of California - Riverside, Entomology, UC Kearney Agricultural Center, 9240 S. Riverbend Ave, Parlier, CA, (3) USDA San Joaquin Valley Agricultural Research Center, 9611 S. Riverbend Ave, Parlier, CA, (4) University of California - Berkeley, Center for Biological Control, Division of Insect Biology (ESPM), Wellman Hall, Berkeley, CA

To define and quantify specific environmental constraints that influence overwintering success of glassy-winged sharpshooter (GWSS), Homalodisca coagulata (Say), laboratory experiments were conducted to determine the effects of constant temperatures on adult GWSS feeding and survival. When provided a plant host, percent adult survival was significantly influenced by temperature and exposure duration with significant interaction between time and treatment. At 21 d exposure, adult survival was < 14% at low temperatures (≤ 8.3oC), but survival was > 73% at 13.3-24.6oC. In a trial comparing host plant presence and absence, adult survival at ≥18.8 oC was highly dependent upon host plant presence, but not at ≤ 8.3 oC. This suggests that GWSS adult feeding does not occur at these low temperatures. Daily feeding, as measured by the production of xylem excreta, is almost nil below 13.3oC, and increases exponentially as temperatures increase from 21.7 to 31.1oC. As temperatures increase beyond 31.1oC, ingestion peaks and declines as temperatures approach 35.1oC. The estimated optimum temperature (with the highest excreta production) and the upper threshold temperature were 33.0 and 36.4oC, respectively. Analysis of data on the percentage of feeding adults suggests that a lower feeding threshold would be around 10.0oC where no adults would produce xylem excreta. Work on better understanding feeding behaviors (i.e., stylet penetration) of GWSS is underway using an electronic penetration graph (EPG). Overall, our findings suggest that lack of feeding at low temperatures would result in greater mortality of overwintering GWSS in field.

Species 1: Hemiptera Cicadellidae Homalodisca coagulata (glassy-winged sharpshooter)