Submitted to: CDFA Pierce's Disease Control Program Research Symposium
Publication Type: Proceedings
Publication Acceptance Date: 10/12/2006
Publication Date: 11/27/2006
Publication URL: http://www.cdfa.ca.gov/pdcp/ Research_Symposium_Index.html
Citation: Johnson, M.W., K. Daane,R. Groves, E.A. Backus. 2006. Spatial population dynamics and overwintering biology of the glassy-winged sharppshooter, Homalodisca coagulata, in California's San Joaquin Valley. CDFA Pierce's Disease Control Program Research Symposium Proceedings. p. 12 Interpretive Summary: The purpose of this project is to determine environmental temperatures that influence glassy-winged sharpshooter (GWSS) population size and winter survival. The production of xylem excretion was used as a measure of GWSS feeding. GWSS individuals held in growth chambers at temperatures ranging from 47 to 88 degrees Fahrenheit increased xylem excretion per adult as temperature increased. The percentage of adults that produced xylem excretion was significantly different among tested temperatures. From 76 to 95 degrees, all adults produced xylem excretion, but the percentage of excreting adults decreased as temperature decreased. At temperatures less than 56 degrees, only 1 of 41 adults produced xylem excretion. Using percent data from 47 to 76 degrees, a mathematical model was devised that showed a direct increase in the percentage of adults that produced xylem excretion with increasing temperature. The lower threshold temperature was 50 degrees, below which no xylem excreta was produced. Results from these experiments will help to define areas in California where GWSS can be expected to overwinter.
Technical Abstract: The purpose of this project is to define specific environmental constraints that influence glassy-winged sharpshooter (GWSS) population dynamics and overwintering success. The production of xylem excreta was used as a measure of GWSS feeding rates. GWSS individuals held at 8.3 to 31.1°C exhibited a positive linear increase in xylem excreta per adult as temperature increased. A low temperature feeding threshold was estimated to be 13.3°C. A Logan Type I model described the relationship between temperature and daily excreta production (mg). The percentage of adults that produced xylem excreta was significantly different among tested temperatures (P < 0.0001), but not between sexes. From 24.6–35.1°C, all adults produced xylem excreta, but the percentage of adults producing excreta declined as temperature decreased. At temperatures 13.3°C, only 1 of 41 adults tested produced xylem excreta. Using percent data from 8.3–24.6°C, a linear increase in the percentage of adults that produced xylem excreta was observed with a lower threshold temperature of 10.0°C, where no xylem excreta was produced. Results from these experiments will be coupled with climatological data to spatially define where GWSS can be expected to overwinter in the agricultural landscape, and identify where continued management efforts should be directed to limit spread into currently non-infested areas.