Optimizing the management of Osmia ribifloris for blueberry pollination

Quality pollination of northern highbush blueberries (Vaccinium corymbosum) is necessary for fruit and seed set. Using honey bees (Apis mellifera) for blueberry pollination presents problems, as bloom phenology and morphology are largely incompatible with honey bee foraging behavior and biology. As such, honey bees alone cannot maximize yields in blueberries. While wild bees can increase yields, achieving enough abundance to service a large field is difficult. A potential solution is managing populations of native bees, particularly those with blueberry specialization. Osmia ribifloris, a native mason bee, nests in man-made shelters, allowing for population management and manipulation. As an Ericaceae specialist and buzz pollinator, O. ribifloris suits blueberry bloom morphology and phenology impeccably. However, O. ribifloris has a high dispersal rate, making managed populations unpredictable. Further work is needed to develop the most effective approach to reducing dispersal and improving management of this species. We manipulated O. ribifloris management strategies across three Oregon blueberry fields to understand which decisions effectively increase nesting rates, and sampled larval pollen provisions in open fields and a closed screenhouse to understand if O. ribifloris primarily collects blueberry pollen in the presence of alternative forage. Our results showcase how new tools and management approaches can improve O. ribifloris nesting rates and add to growing evidence that it uses blueberry pollen as a primary nutritional resource. These findings indicate that a monocultural landscape is likely not the primary driver of dispersal in this species and that nesting rates can be improved with better management.