Optimal foraging by honey bees (<i>Apis mellifera</i>) reduces cross-cultivar visitation inhighbush blueberry (<i>Vaccinium corymbosum</i>): implications for pollinationefficiency in monocultures

Abstract

Inter-cultivar pollination is essential for high-quality blueberry production, as it increases both fruit set and fruit size. In commercial orchards, this is often achieved by alternating blueberry cultivars across rows, based on the assumption that honey bees move pollen between cultivars by switching rows. However, honey bee movement patterns in orchards remain understudied, and it is unclear whether this design effectively supports inter-cultivar pollination. To address this knowledge gap in a South African context, we determined the frequency of honey bee foraging movements across versus along blueberry rows. While observing a focal foraging honey bee, we recorded the number of flowers visited on a blueberry bush, whether the bee transitioned between plants, and whether these transitions occurred along or across a row. Our observations revealed that honey bees predominantly foraged along rows (over 90% of transitions), rarely switching across rows. Consequently, alternating cultivars by row is likely to limit inter-cultivar pollination in South African blueberry orchards, potentially reducing yield. We recommend interplanting compatible cultivars within rows to enhance pollen transfer and fruit production. Given that honey bees are used globally as the primary managed pollinator, similar movement patterns may occur in other regions, suggesting that modifying planting designs could increase yields of blueberries and other bee-pollinated crops with minimal additional cost. However, these findings are based on observations from a single commercial orchard and should be replicated across multiple farms and environmental conditions to determine the generality of these patterns.