BEES ARE THE MOST IMPORTANT POLLINATORS OF BOTH WILD PLANTS AND AGRICULTURAL CROPS. ON AN ANNUAL BASIS, BEE POLLINATION CONTRIBUTES $170B TO THE GLOBAL ECONOMY AND AN ESTIMATED $15.1B TO US AGRICULTURAL PRODUCTION. BOTH WILD AND MANAGED BEES ARE PARTICULARLY IMPORTANT FOR THE HIGH-VALUE, SPECIALTY CROPS PRODUCED IN THE EASTERN US. APPLES, CHERRIES, PEACHES, PLUMS, CRANBERRIES, STRAWBERRIES, CUCURBITS, AND CANE FRUITS ARE ALL DEPENDENT ON THE POLLINATION SERVICES OF BEES. OVER THE PAST 10 YEARS A GROWING BODY OF SCIENTIFIC EVIDENCE INDICATES THAT WILD, MOSTLY SOLITARY, BEES CONTRIBUTE SIGNIFICANTLY TO HIGH VALUE, SPECIALTY CROP POLLINATION IN THE US.BUT THE POLLINATION SERVICES THAT WILD BEES PROVIDE ARE VULNERABLE. OUR PREVIOUS WORK HAS SHOWN THAT CHANGES IN BOTH LANDSCAPE AND PESTICIDE USE CAN IMPACT THE ABUNDANCE AND SPECIES RICHNESS OF WILD BEES IN AGROECOSYSTEMS IN NEW YORK AND WISCONSIN. FUNGICIDES, IN PARTICULAR, WERE FOUND TO HAVE A NEGATIVE IMPACT ON THE WILD BEE COMMUNITY. THIS IS A PUZZLING RESULT BECAUSE FUNGICIDES ARE CONSIDERED TO HAVE LOW DIRECT TOXICITY TO BEES (AS MEASURED BY LD50 VALUES OBTAINED FOR ADULT HONEY BEE WORKERS).ONE POSSIBLE MECHANISM BY WHICH FUNGICIDES ARE IMPACTING WILD BEES MAY BE VIA THEIR IMPACTS ON THE BROOD CELL MICROBIOME. THE BROOD CELL MICROBIOME REFERS TO THE BACTERIA AND FUNGI THAT LIVE WITHIN THE POLLEN PROVISIONS OF SOLITARY AND SOCIAL BEES. WE KNOW FROM PREVIOUS STUDIES AND OUR OWN WORK THAT THE POLLEN AND NECTAR PROVISIONS OF SOLITARY BEES HOST A DIVERSE COMMUNITY OF BOTH BACTERIA AND FUNGI. IN PEPONAPIS PRUINOSA, THE SQUASH BEE, WE DOCUMENTED 160 BACTERIA AND 240 FUNGAL SPECIES IN POLLEN PROVISIONS ACROSS SITES IN UPSTATE NY. WORK BY SHAWN STEFFAN AND COLLEAGUES AT THE UNIVERSITY OF WISCONSIN HAS SHOWN THAT THESE MICROBES PLAY AN IMPORTANT ROLE IN THE LARVAL DIET OF BEES. BEE LARVAE ARE CONSUMING AND ASSIMILATING PROTEINS, CARBOHYDRATES, LIPIDS AND OTHER NUTRIENTS FROM THESE MICROBES AND FUNGICIDES MAY DISRUPT THIS MICROBIAL COMMUNITY IN WAYS THAT IMPACT BEE NUTRITION AND ULTIMATELY LARVAL DEVELOPMENT.WE PROPOSE TO DELVE DEEPLY INTO HOW FUNGICIDES AND OTHER AGROCHEMICALS IMPACT THE MICROBIAL COMMUNITY OF THE POLLEN PROVISIONS FOUR IMPORTANT WILD POLLINATORS: BOMBUS IMPATIENS (THE COMMON EASTERN BUMBLEBEE), PEPONAPIS PRUINOSA (THE SQUASH BEE), OSMIA CORNIFRONS (THE HORN-FACED BEE) AND OSMIA RIBIFLORIS (THE BLUEBERRY BEE). OUR FOCAL BEE SPECIES ARE IMPORTANT POLLINATORS OF MANY CROPS, INCLUDING CUCURBITS, FLOWERING FRUIT TREES, BLUEBERRIES, AND MANY OTHERS. WE HAVE CHOSEN BEES THAT SPAN A RANGE OF LIFE HISTORIES, INCLUDING ONE SOLITARY, GROUND-NESTER (PEPONAPIS PRUINOSA; APIDAE), TWO ABOVE-GROUND, CAVITY NESTERS (OSMIA CORNIFRONS AND O. RIBIFLORIS; MEGACHILIDAE), AND ONE CAVITY-NESTING SOCIAL BEE (BOMBUS IMPATIENS: APIDAE). THESE BEE SPECIES RANGE FROM NARROW HOST-PLANT SPECIALISTS (PEPONAPIS PRUINOSA AND OSMIA RIBIFLORIS) TO BROAD, HOST-PLANT GENERALISTS (OSMIA CORNIFRONS AND BOMBUS IMPATIENS). OUR RANGE OF TAXA INCLUDE MASS-PROVISIONING SOLITARY BEES (PEPONAPIS, OSMIA) AND PROGRESSIVELY PROVISIONING SOCIAL BEES (BOMBUS).WE HAVE CONSIDERABLE EXPERTISE WORKING ON THESE BEE SPECIES. THROUGH THE USE OF METAGENOMIC METHODS (16S AND ITS AMPLICON SEQUENCING AND RNA-SEQ), THE USE OF STABLE ISOTOPES TO IDENTIFY TROPHIC LEVEL, AND CAREFUL MANIPULATIVE LABORATORY EXPERIMENTS, WE PROPOSE TO EXPLORE HOW FUNGICIDES MODIFY THE NATURAL MICROBIAL COMMUNITY AND HOW PERTURBATIONS OF THE MICROBIAL COMMUNITY IMPACT BEE LARVAL DEVELOPMENT.OUR PROJECT WILL CONTRIBUTE SIGNIFICANTLY TO OUR UNDERSTANDING OF THE IMPACTS OF FUNGICIDES ON BEE HEALTH. WE WILL DOCUMENT FOR THE FIRST TIME THE DIVERSITY OF MICROBIAL ASSOCIATES IN THE FOUR FOCAL BEE SPECIES, WE WILL DETERMINE THE CONTRIBUTION OF THESE MICROBES TO BEE NUTRITION, AND WE WILL EXPERIMENTALLY MANIPULATE THE BROOD CELL MICROBIOME IN ORDER TO UNDERSTAND HOW PERTURBATIONS IN MICROBIAL COMMUNITY IMPACT LARVAL DEVELOPMENT. OUR RESULTS WILL HAVE IMPACTS ONOUR UNDERSTANDING OF THE BASIC BIOLOGY OF BEES, ON POLICIES GOVERNING PESTICIDE USE AND ON BEST-MANAGEMENT PRACTICES, AND ON THE HEALTH OF FARMERS AND THE WORKERS WHO CONTRIBUTE TO CROP PRODUCTION ACROSS THE US.