WITH A FARM GATE VALUE OF MORE THAN 5 BILLION DOLLARS, WINE GRAPES ARE A LEADING U.S. COMMODITY. THE PROFITABILITY OF THIS INDUSTRY IS THREATENED BY GRAPEVINE RED BLOTCH ASSOCIATED VIRUS (GRBAV) WHICH CAUSES GRAPEVINE RED BLOTCH DISEASE (GRBD). THIS NEWLY IDENTIFIED VINEYARD PATHOGEN CAUSES VINE DAMAGE SIMILAR TO GRAPE LEAFROLL DISEASES AND IS SPREAD BY INSECTS. RECENT STUDIES SUGGEST THAT THE CALIFORNIA VECTOR IS A MEMBRACID (SAP-SUCKING TREEHOPPERS), THE THREE-CORNERED ALFALFA HOPPER (TCAH; SPISSISTILUSFESTINUS). OUR GOAL IS TO EVALUATE THE ROLE OF TCAH AND OTHER INSECT VECTORS IN DISPERSAL OF GRBAV. WE WILL FIRST EXAMINE THE BIOLOGY OF TCAH AND OTHER CANDIDATE INSECTS TO DETERMINE IF THEY ARE ABLE TO PICK UP, CARRY, AND SPREAD GRBAV THROUGH VINEYARDS. WE WILL THEN STUDY THE ECOLOGY OF IDENTIFIED INSECT VECTORS TO DETERMINE WHEN THEY MOVE FROM SURROUNDING NATURAL HABITATS INTO THE VINEYARD, WHERE THEY OVERWINTER, THE FEEDING DAMAGE THEY CAUSE, AND THETIMING AND PATTERN OF GRBAV TRANSMISSION AND SPREAD AMONG VINES. COMPLETION OF THIS WORK WILL PROVIDE CRITICAL INFORMATION ON GRBD EPIDEMIOLOGY AND AID IN THE DEVELOPMENT OF AN OPTIMIZED, COST-EFFECTIVE INSECT VECTOR-VIRUS-DISEASE CONTROL PROGRAM.