2006 Annual Report 4d.Progress report. This report serves to document research conducted under a Trust Agreement between ARS and Frito Lay, Inc. This research is integrated with objectives in the parent CRIS 6204-22000-018-00D, Biological Control of Invasive and Exotic Pests, to discover and evaluate natural enemies of the glassy-winged sharpshooter (GWSS). This project was initiated in FY 2006 to investigate the potential of glassy-winged sharpshooters, leafhoppers, and potato psyllids as potential vectors of zebra chip in potatoes. The xylem inhabiting bacterium, Xylella fastidiosa, that is the causal agent for Pierce's disease in grapes also appears to be inducing zebra chip in potatoes. A survey for potential insect vectors of X. fastidiosa was conducted in zebra-chip impacted commercial potato fields located near McAllen, TX. Native and weedy plants were analyzed for the presence of X. fastidiosa to determine if they could be potential reservoirs for this pathogen in the surrounding environment. Potato psyllids and B. cockerelli were the most common insects collected in the study. Psyllids began to enter the fields in mid-January and reached a peak. A high percentage of the psyllids tested positive for X. fastidiosa. The potato leafhopper, Empoasca spp., and green leafhopper, Penestragania sp., were common throughout the season, and more than half of the insects tested were positive for X. fastidiosa. Other leafhoppers, Scaphytopius sp., Ceratogallia sp., and Erythroneura sp., were common throughout the season, but a lower percentage were positive for X. fastidiosa. Very few sharpshooters were collected in the survey, and almost all were positive for X. fastidiosa. Of the 13 plant species tested for X. fastidiosa, only one, climbing milkweed vine, Funastrum clausum, was positive for the bacterium. Climbing milkweed vine is common in the inundated lagunas near the potato fields. Additional studies are planned for the 2007 field season in cooperation with Frito Lay, Inc. A team of scientists from ARS-Weslaco and Yakima, North Dakota State University, and the University of Texas have submitted a proposal to USDA-CSREES-NRI (National Research Initiative) to investigate the role of X. fastidiosa as the causal agent of zebra chip in potatoes and determine the transmission epidemiology of this disease by potential insect vectors.