High tunnel production of overwintering strawberries is becoming increasingly popular because this method allows growers to access early-season market prices with high quality fruits. Overall strawberry yield is dependent on sufficient pollination. This presents a particular challenge for overwintering strawberries because the crop begins flowering before the emergence of most bee pollinators; however, flies are often abundant in high tunnels, even in colder months. Further, flies have been identified as important pollinators of strawberries in previous work. In this study, we evaluate the pollination services provided by flies for overwintering strawberries in high tunnels and assess the efficacy of using sweet alyssum as a companion plant to increase fly recruitment into the high tunnels. In control tunnels, strawberries were grown as a monoculture, while in treatment tunnels, they were interplanted with sweet alyssum. To evaluate fly pollination services, eight co-flowering strawberry buds were selected in each tunnel. Four buds were assigned to an ‘open-pollinated’ treatment where pollinators could freely visit the flowers. The remaining four buds were assigned to a ‘self-pollination’ treatment where buds were enveloped in mesh bags to exclude pollinators. All fruits from these flowers were weighed and evaluated for quality to assess pollination services. Finally, sticky cards were deployed in all high tunnels to compare fly recruitment between treatments. Total strawberry yield was measured in all tunnels to determine the economic benefit of planting sweet alyssum with strawberries. This study has the potential to help growers increase pollination of early blooming strawberries in high tunnels.
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