Bumble bees do it better: the importance of wild bees for the pollination of Haskap crops

Haskap (Lonicera caerulea) is an early flowering, insect pollinated and self-incompatible fruit crop with a unique floral structure, in which the berry is a compound fruit formed from the ovaries and fused bracteoles of the two-flowered inflorescence. Currently, honey bees (Apis mellifera) and blue orchard bees (Osmia lignaria) are used as managed pollinators for Haskap, but their efficacy as Haskap pollinators is unknown.  In this study, we compared the effectiveness and efficiency of these two species to wild bumble bees (Bombus sp.) to determine which of these three groups of bees is the best pollinator of Haskap, which will help managers make decisions about how to maximize pollination and fruit yield. We combined floral characteristics with data on single visit deposition and behaviour data (visit symmetry, visitation rate, activity levels and pollen load composition) in order to assess which taxon contributes the most to Haskap pollination on an individual level. We found that bumble bees are the most effective and efficient pollinators of Haskap; in addition to their tolerance of cool weather conditions, they were the only group to deposit significantly more pollen on the stigma than unvisited controls, they could visit the most flowers per time interval, and they showed high levels of floral constancy on Haskap. By providing year-round forage and nesting habitat for bumble bees and other native species, Haskap growers can increase their fruit yield and help to secure pollination services into the future.