PS 48-250 - Pollinator diversity in urban orchards

Abstract: Urban orchards as an agricultural system are not as well understood as their rural, commercial counterparts. Urban orchards are smaller and have higher crop diversity. Thus, research conducted within rural orchards may not translate to an urban context. Additionally, urban orchards are often part of food sustenance programs and thus fruit yield has direct effects on the people who rely on them for their produce. Many orchards in urban systems exhibit large interannual variation in fruit yields. It is hypothesized that this variation may be due to the lack of pollination services. Most orchard fruit trees require cross-pollination to reproduce, which is mainly conducted by bees and flies. We examined the pollinator community present in 12 urban orchards in St. Louis, Missouri. The urban orchards contained an average of 18 trees and 5 fruit types. Five of our orchards have managed Apis mellifera hives on site. We sampled pollinators via aerial netting four to six times throughout the flowering season of 2022. Sampling events in each orchard were carried out by netting flower visiting insects on each blooming fruit tree for five minutes. We examined the bee diversity for orchards overall as well as how diversity varied between individual orchards.
We collected 30 insect species in the 2022 growing season. Bees comprised an average of eighty percent of insects collected overall. The next most common insect pollinator collected were flies at seventeen percent, and all other insects were three percent. Bees in the genus Andrena comprised the largest percentage of insects collected in forty-six percent of sampling events. Preliminary results suggest that Andrena are the most prevalent genus in our urban orchards, even when honeybee hives were present at the orchard. With these baseline data, it is unclear if overall bee abundance could be a limiting factor for fruit production. We will continue to sample orchards for the next two years. We are also investigating if supplementing bees will have an effect on pollinator abundance in the future of this study. These results will help inform urban orchard management, and thus increase food security, by making expected yields more reliable.