SPATIAL AND TEMPORAL RELATIONS BETWEEN GLASSY-WINGED SHARPSHOOTER SURVIVAL AND MOVEMENT, XYLEM FLUX PATTERNS AND XYLEM CHEMISTRY IN DIFFERENT HOST PLANTS

• Author(s): Hoddle, Mark; Luck, Robert; Andersen, Peter; Coviella, Carlos;
• Abstract: The glassy-winged sharpshooter (GWSS), Homalodisca coagulata (Say) (Homoptera: Cicadellidae), has been identified as the principal vector for the xylem restricted bacterium, Xylella fastidiosa, the causal agent of Pierces and other related diseases. Pierces disease is threatening Californias wine and grape industry, and has already inflicted heavy damage to certain areas of the state. Our project seeks to identify those aspects in the GWSS-host plant interaction that explain variations in GWSS density and performance (i.e., immature survival and adult reproduction), that is, its population dynamics. Following a species population dynamics requires a reliable and accurate method of estimating its field densities. Currently, such estimates rely mainly on yellow sticky traps or net beatings with subsequent insect counts. We lack a means of calibrating these density estimates. Thus, as a first step in our study, we have developed a method of estimating GWSS populations in a tree using an absolute sampling method. Using a parachute to cover a citrus tree, we fog it to recover from it all GWSS stadia except eggs. We correlate GWSS densities from this method with those using the standard yellow sticky traps and net beatings for adult GWSS. We will present data on density estimates for this insect, in regions of the state heavily infested with GWSS. A second aspect of our research seeks to determine host plant choice and the density of GWSS on the host plant. We will use a specially designed Schlander bomb to measure xylem fluid pressure and to extract xylem fluid for chemical analyses. We will use this technique to explore possible correlations between changes in GWSS density and reproduction on a host plant and its relationship to physical and chemical properties of that plant. These techniques will give us insight into host plant choice by GWSS.
• Publication Date: Dec 2001
• Journal: 2001 Pierce's Disease Research Symposium