RELATIONSHIPS BETWEEN TOTAL POPULATION COUNTS OF GLASSY-WINGED SHARPSHOOTERS AND NUMBERS OBTAINED FROM VARIOUS SAMPLING METHODS

• Author(s): Blua, Matthew; Redak, Richard; Akey, David; Coviella, Carlos;
• Abstract: We seek to understand the way in which commonly used sampling methods work, in relation with real population densities. We used short citrus experimental trees and commercial-size ones, in order to encompass most of the size range of plants that are important hosts to GWSS. At the University of California, Agricultural Operations, Riverside, California, we conducted two series of experiments in citrus with natural GWSS populations. The trees were 2 m tall navel oranges that have been blocked, shaped, and skirted for uniformity within the block, as well as commercial-sized citrus trees. We compared visual counts (adults and nymphs), beat-net (adults, early nymphs and late nymphs), and yellow sticky cards (adults), with the absolute GWSS density for each tree using the tent-fogging methodology. We used fluorescent colored dust to mark 100 GWSS released inside the tents to determine the percentage recovery. These surveys were conducted every other week from June 2002 through September 2003. The results showed significant correlations between the methods and real population densities, with R(2) values that ranged from 0.19 to 0.84. The results how that correlations are better from small trees and bushes, but also that for commercial-size trees most of the methods can explain close to 50% of the real population size. We seek now to include temperature, wind, rain, and cloud coverage data to a multivariate analysis in order to explore whether that would improve the correlations, and thus to better assess the predictive value of the most commonly used sampling methods for GWSS.
• Publication Date: Aug 2003
• Journal: 2003 Pierce's Disease Research Symposium