Nocturnal pollination is equally important as, and complementary to, diurnal pollination for strawberry fruit production

Abstract

Declining insect populations and their associated pollination services to crops raise concerns for global food security. While most studies focus on the contribution of diurnal pollinators to crop yields, nocturnal pollination receives little attention. In this study, we used a randomised block design (n = 6) in the open ground to determine the relative contribution of nocturnal and diurnal pollination to strawberry yield. We found that, on average, there was no effect of insect pollination (nocturnal, diurnal, or both) on total number of fruits and total weight of fruits harvested per plant. However, when plants produced many fruits, night-pollinated and open-pollinated plants increased total fruit weight per plant, compared to plants that received no pollinators. Furthermore, compared to the no-pollinators treatment, individual fruit weight (g) was significantly higher in night-pollinated plants (27% higher) and open-pollinated plants (46% higher), whereas the day-pollinated treatment (17% higher) did not significantly differ from no-pollinators and night-pollinated plants. Fruit diameter (mm) followed a similar pattern. Fruit sweetness (%total soluble solids) was highest in the no-pollinated treatment, and other treatments did not differ from each other. The average fruit shape was of significantly poorer quality in the no-pollinators treatment than any of the other treatments, which did not significantly differ from each other, but did show a trend of fewer poorly shaped fruits. Overall, nocturnal pollination was at least equally important as, and highly complementary to diurnal pollination for determining strawberry fruit quality. However, we do not know the identity of the nocturnal pollinators. Nevertheless, nocturnal pollination seems to be an important, but overlooked part of the contribution to insect pollination to crop yield.