Solitary bees reduce pollination and production deficits in apple cultivation

Low pollinator richness and abundance is a primary driver of pollination deficits and may lead to reduced yields (production deficits). In response, domesticated honeybees are often used to increase pollination success, even though honeybees are less efficient pollinators than naturally occurring wild bees. Here, we explored whether Norwegian apple orchards experience pollination and production deficits, and if such deficits could be related to specific pollinator groups and activity. We conducted a supplemental pollination experiment and measured seed set and yield (fruit set x weight) for three cultivars, in six orchards, in two distinct apple growing regions in central Norway, for two years. In addition, we used cameras to record relative pollinator activity throughout the flowering period. Overall, we found a pollination and production deficit across all cultivars, although there were differences in pollination deficit among cultivars. Three orchards had a pollination deficit both years of the study, suggesting sub-optimal orchard structure and/or a lack of pollinators. However, we found that solitary bees significantly reduced both pollination and production deficit, suggesting that orchard management actions should focus on increasing wild bee diversity and abundance. • Norwegian apple orchards experience pollination and production deficits. • The degree of deficit varies between cultivars and years. • Aroma has higher pollination deficit and may come with financial risk for growers. • Solitary bee activity decreased pollination and production deficits. • Cultivar placement and management actions are important drivers of deficits.