THE UNITED STATES (US) PRODUCES APPROXIMATELY 6% OF THE WORLD'S APPLES WITH A UTILIZED PRODUCTION VALUE OF $3.4 BILLION ANNUALLY. TO REMAIN COMPETITIVE, US APPLE GROWERS ARE TRANSITIONING FROM LARGE-TREE, LOW-DENSITY PLANTING SYSTEMS (&LE; 500 TREES/HA) TO HIGH-DENSITY (HD) TRELLISED SYSTEMS (2,500-5,000 TREES/HA) ON DWARFING ROOTSTOCKS. HD SYSTEMS CAN CONFER SIGNIFICANT ECONOMIC BENEFITS TO APPLE PRODUCERS INCLUDING EARLIER FRUIT PRODUCTION, IMPROVED FRUIT QUALITY, IMPROVED LAND USE EFFICIENCY, DECREASED LABOR INPUTS, AND COMPATIBILITY WITH NEW ORCHARD TECHNOLOGIES. HOWEVER, PRODUCTION CHALLENGES LEADING TO TREE MORTALITY CAN LEAD TO CATASTROPHIC FINANCIAL LOSSES. RAPID APPLE DECLINE (RAD) A SEVERE THREAT TO THE EASTERN US APPLE INDUSTRY AND A DEVELOPING THREAT TO THE MID-CENTRAL US APPLE INDUSTRY, INVOLVES THE INTERACTION OF ABIOTIC AND BIOTIC FACTORS THAT CAUSE THE SUDDEN COLLAPSE AND DEATH OF YOUNG (&LE; 6 YEARS) TREES IN HD SYSTEMS. ORIGINALLY REPORTED IN 2013 IN SEVERAL ORCHARDS IN PA AND NY, RAD HAS BEEN OBSERVED IN APPLE PRODUCING STATES THROUGHOUT THE SOUTHEAST, MID-ATLANTIC, NEW ENGLAND, MICHIGAN, AS WELL AS IN ONTARIO, CANADA. IN 2017, 80% OF HD ORCHARDS IN WESTERN NC HAD TREES WITH RAD SYMPTOMS, AND OFTEN &GT;30% OF TREES WITHIN ORCHARDS WERE AFFECTED. HIGH RATES OF TREE MORTALITY CAN RESULT IN CONSIDERABLE ECONOMIC LOSSES. SUCH TREE MORTALITY NOT ONLY HAS IMMEDIATE FINANCIAL IMPLICATIONS FOR GROWERS, BUT ALSO CAUSES UNPRECEDENTED DELAYS AND LOSSES OF FUTURE PROFITS. INFESTATION BY AMBROSIA BEETLES HAS FREQUENTLY BEEN ASSOCIATED WITH RAD. UNLIKE OTHER WOOD-BORING INSECTS, AMBROSIA BEETLES ARE "FUNGUS FARMERS" THAT CULTIVATE GARDENS OF SYMBIOTIC FUNGI TO SERVE AS FOOD FOR ADULTS AND OFFSPRING. THESE FUNGI, ALONG WITH AUXILIARY FUNGI ON BEETLE EXOSKELETONS, COLONIZE THE VASCULAR TISSUE OF APPLE TREES. AMBROSIA BEETLES AND OPPORTUNISTIC FUNGAL PATHOGENS REQUIRE A TREE TO BE STRESSED TO CAUSE APPRECIABLE TREE DECLINE. DUE TO THE CRYPTIC LIFE HISTORY OFAMBROSIA BEETLES AND OPPORTUNISTIC FUNGAL PATHOGENS AND THE CHALLENGES OF IDENTIFYING HOST PHYSIOLOGICAL HEALTH STATUS, EXCLUSIVE RELIANCE ON INSECTICIDAL CONTROL OF AMBROSIA BEETLES IS NOT A VIABLE MANAGEMENT OPTION. AN INTEGRATED APPROACH THAT INCLUDES CULTURAL PRACTICES TO MINIMIZE TREE STRESS, BEHAVIORAL-BASED MANAGEMENT OF BEETLES, AND TIMELY PESTICIDE APPLICATIONS WILL BE NECESSARY TO MITIGATE THE EFFECTS OF AMBROSIA BEETLE ASSOCIATED RAD IN THE EASTERN US. THIS PROPOSAL AIMS TO DEVELOP INTEGRATED MANAGEMENT STRATEGIES TO MITIGATE AMBROSIA BEETLE ASSOCIATED RAPID APPLE DECLINE IN HUMID APPLE PRODUCTION REGIONS OF THE US. USING A TRANSDISCIPLINARY APPROACH, RESEARCH FROM THIS PROPOSAL WILL CONTRIBUTE TO THE DEVELOPMENT OF RECOMMENDATIONS THAT INCORPORATE MANAGEMENT OF AMBROSIA BEETLES AND THEIR ASSOCIATED FUNGI WITH THE QUANTIFICATION OF TREE HEALTH INDICATORS. STAKEHOLDER INVOLVEMENT WILL BE PRESENT THROUGHOUT THIS PROJECT THROUGH ON-FARM DEMONSTRATION TRIALS, PARTICIPATION WITHAMBROSIA BEETLE TRAPPING, AND THROUGH PARTICIPATION ON A STAKEHOLDER ADVISORY PANEL TO ASSIST IN DISSEMINATION OF PROJECT DELIVERABLES AND PROJECT ASSESSMENT. DIRECT IMMEDIATE BENEFICIARIES FROM THIS PROJECT INCLUDE COMMERCIAL APPLE GROWERS IN THE EASTERN US; HOWEVER, RESEARCH-BASED RECOMMENDATIONS THAT ARE DEVELOPED WILL BE OF VALUE TO APPLE GROWERS IN THE MIDWEST, WEST, AND PACIFIC NORTHWEST. THE LONG-TERM GOALS OF THIS PROJECT ARE TO CONTRIBUTE TOWARDS ADDRESSING AN AFRI IDENTIFIED KEY PROBLEM: MITIGATING IMPACTS OF BIOTIC AND ABIOTIC CONSTRAINTS ON FOOD PRODUCTION.