Characterizing bee communities and pollen limitation in Indiana specialty crops

Lack of adequate pollination limits yield in many specialty crops, and this pollen limitation is determined by crop pollination requirements and pollinator community dynamics. Bee communities and degree of pollen limitation is variable between crops and regions, necessitating a crop-specific, regional approach to describing pollination services. Despite primarily producing agronomic crops, Indiana produces a wide variety of specialty crops, including apples, blueberries, watermelons, and tomatoes (grown for processing in open fields and fresh market in high tunnels). Each crop has variable bloom phenology, pollination requirements, and associated management practices (e.g., thinning in apples and protective cover in high tunnels), with potential implications for their pollinator communities and pollination services. This thesis aims to 1) use flower observations and pan traps to compare pollinator communities between crops, including the contributions of managed and wild bees, community diversity, and composition and 2) assess pollen limitation in each crop using pollination experiments. The study took place on commercial farms throughout Indiana over the course of three summers (2022-2024). We found that distinct pollinator communities persisted in each crop system, with spring-blooming apples and blueberries dominated by honey bees (Apis mellifera) and summer-blooming tomatoes and watermelons dominated by wild bees, particularly Bombus spp. in tomatoes and Lasioglossum spp. in watermelon. We also found evidence of pollen limitation with respect to fruit set in all crop systems except for apples (measured at harvest, after apple thinning occurred). Evidence of pollen limitation with respect to fruit weight was detected only in field tomatoes and apples, but not other crops. Meanwhile, insect pollination increased fruit set and weight in almost every crop, except for high tunnel tomatoes, implying reduced pollination services in this semi-protected system. Our results highlight the importance of protecting wild pollinator communities in Indiana, particularly in watermelons and tomatoes, and identify yield gaps in multiple crops, especially tomatoes, which could be addressed by increasing pollination services. This crop-specific information is a valuable first step in encouraging growers to adopt pollinator friendly management decisions and protecting pollination services in Indiana.