**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** GRAPEVINE RED BLOTCH VIRUS (GRBV) IS OF CONCERN TO THE GRAPE AND WINE INDUSTRIES IN THE UNITED STATES. CONSEQUENCES OF INFECTION INCLUDE REDUCTION IN FRUIT YIELD AND QUALITY AND CAN CAUSE ECONOMIC LOSSES RANGING BETWEEN $2,213 TO $68,548 PER HECTARE OVER A 25-YEAR LIFESPAN OF A VINEYARD. THE THREE-CORNERED ALFALFA HOPPER, SPISSISTILUS FESTINUS, TRANSMITS GRBV FROM GRAPEVINE TO GRAPEVINE IN THE VINEYARD BUT LITTLE IS KNOWN ABOUT ITS PHENOLOGY AND BEHAVIOR IN A VINEYARD ECOSYSTEM. FOR EXAMPLE, NO INFORMATION IS AVAILABLE ON PREFERRED FEEDING AND REPRODUCTIVE HOSTS OF S. FESTINUS IN VINEYARDS. INFORMATION ON S. FESTINUS ECOLOGY IS ALMOST EXCLUSIVELY OBTAINED FROM LEGUME CROPS SUCH AS SOYBEAN, ALFALFA, PEANUTS, WHICH S. FESTINUS IS A PEST OF IN THE SOUTHERN U.S. THE FACT THAT SOME LEGUMES LIKE SWEET PEA, VETCH, TREFOIL, COWPEA, AND CLOVER ARE USED IN VINEYARD COVER CROP MIXTURES HOLD HIGH PRECEDENCE IN THE SEARCH FOR CANDIDATES OF FEEDING AND REPRODUCTIVE HOSTS OF S. FESTINUS. PLANTS FROMTHE FABACEAE FAMILY HAVE PREVIOUSLY BEEN COLLECTED IN THE VINEYARD ECOSYSTEM AND TESTED FOR GRBV. ALL HAVE TESTED NEGATIVE FOR GRBV, SUGGESTING A LIMITED, IF ANY, ROLE IN SECONDARY VIRUS SPREAD (CIENIEWICZ ET AL. 2019, WILSON ET AL. 2020). NONETHELESS, REMOVING OR TILLING THESE LEGUMES IN VINEYARD SETTINGS HAS BEEN SHOWN TO REDUCE VISIBLE POPULATIONS OF S. FESTINUS IN THE CANOPY OF GRAPEVINES (BICK ET AL. 2020, WILSON ET AL. 2020). UNFORTUNATELY, THIS PRACTICE IS NOT KNOWN TO REDUCE THE RATE OF GRBV TRANSMISSION. WITHOUT FURTHER GUIDANCE AND UNDERSTANDING OF THE INTERACTIONS BETWEEN S. FESTINUS AND FEEDING AND REPRODUCTIVE HOSTS, GROWERS CONTINUE TO IMPLEMENT THIS LABOR-INTENSIVE STRATEGY, WITH LITTLE TO NO PROMISE FOR ANY BENEFITS WITH REGARDS TO LIMITED DISEASE SPREAD.S. FESTINUS ARE PRESENT IN VINEYARDS IN NAPA VALLEY, CA DURING EARLY TO MID-SUMMER (CIENIEWICZ ET AL. 2018; WILSON ET AL. 2020). THIS TIMEFRAME DOES NOT CORRESPOND WITH OPTIMAL DISEASE SYMPTOM EXPRESSION AND HIGHEST GRBV TITER ON V. VINIFERA THOUGH, WHICH OCCURS IN OCTOBER-NOVEMBER (CIENIEWICZ ET AL. 2020). NONETHELESS, IN FREE-LIVING VINES, VIRAL TITER IS SUSPECTED TO BE EARLIER, CORRESPONDING MORE CLOSELY TO THE TIMING OF S. FESTINUS' MORE ACTIVE MONTHS IN A VINEYARD SETTING. A FOREST AREA EDGING A STUDY VINEYARD WAS FOUND TO HARBOR FREE-LIVING VINES INFECTED WITH GRBV (PERRY ET AL. 2016). THIS, COUPLED WITH THE FACT THAT THERE WAS SIGNIFICANT VINEYARD EDGE EFFECT FOR SPREAD (CIENIEWICZ ET AL. 2017; DALTON ET AL. 2019), MAKES IT QUITE LIKELY THAT FREE-LIVING VINES ARE FED ON BY S. FESTINUS COMING OUT OF DIAPAUSE AND THEN SPREADING TO THE VINEYARDS COME JUNE WHEN THEY BEGIN SCOUTING FOR REPRODUCTIVE HOSTS. DETERMINING THESE VIRUS-VECTOR-HOST INTERACTIONS WILL SHAPE OUR KNOWLEDGE OF S. FESTINUS ECOLOGY AND DISEASE EPIDEMIOLOGY, WHICH IN TURN, WILL INFORM THE DEVELOPMENT OF NOVEL DISEASE MANAGEMENT STRATEGIES.ALL IN ALL, THE RELATIONSHIP BETWEEN S. FESTINUS AND V. VINIFERA IS UNPRECEDENT. THE RECE,NT DISCOVERY OF AN EXTENDED ACQUISITION OF 10 DAYS FOR GRBV TO REACH THE SALIVARY GLANDS OF S. FESTINUS (FLASCO ET AL. 2021) AND POTENTIALLY A LONGER PERIOD FOR TRANSMISSION TO OCCUR, COUPLED WITH THE CONFIRMATION OF S. FESTINUS AS A VECTOR OF EPIDEMIOLOGICAL RELEVANCE IN THE VINEYARD (FLASCO ET AL. 2023), DRIVES A NEED FOR UNDERSTANDING THE MODALITY BEHIND THE ECOLOGY OF S. FESTINUS IN VINEYARDS MORE THAN EVER. BY USING SURVEILLANCE AND SCOUTING METHODS, ALONGSIDE S. FESTINUS GUT CONTENT ANALYSES TO TRACK DIETARY HISTORY, PLUS BEHAVIOR STUDIES ON DIFFERENT GRAPE SPECIES, WE WILL STUDY HOW THE ECOLOGICAL COMMUNITY OF S. FESTINUS AFFECTS THE SPREAD OF GRBV IN VINEYARDS. THE FINDINGS OF THIS PROJECT WILL PROVIDE NEW INSIGHTS INTO THE GRBV EPIDEMIOLOGY AND WILL BE PERTINENT FOR PROVIDING GROWERS WITH INFORMED DISEASE MANAGEMENT STRATEGIES.