Positive effects of the pollinators Osmia cornuta (Megachilidae) and Lucilia sericata (Calliphoridae) on strawberry quality

In the last decades, the fraction of crops requiring biotic pollination has increased dramatically. While wind- and self-pollination is possible for some of these crops, insect pollination generally increases yields and quality of produce. Especially pollinator communities with varying traits often show additive, positive effects on crop pollination. The aim of this study was to investigate the effect of two pollinator species with contrasting life history traits, the European orchard bee, Osmia cornuta, and the green bottle fly, Luciana sericata, on fruit quality, namely size, weight, shape, and color of fruits of the garden strawberry, Fragaria x ananassa We hypothesized that (1) pollination by both species individually results in higher strawberry quality compared to wind- and self-pollination, and (2) combining both species for pollination leads to higher strawberry quality due to higher functional diversity. To test these hypotheses, we used 40 mesh cages, each containing six strawberry plants. Flowering strawberry plants were either exposed to four O. cornuta individuals, four L. sericata individuals, two individuals of each species, or no pollinators (control) for one week. Fruit weight was only significantly higher than the control treatment when strawberry plants were exposed to bees. Fruit deformation, however, significantly decreased with all three pollinator treatments. Strawberry quality in cages with a combination of bees and flies was not superior to strawberry quality in cages with bees alone. Our results highlight the importance of insect pollination for strawberry quality but increased functional diversity of pollinators did not lead to additive pollination effects.