The effect of plastic low tunnels on natural enemies and pollinators in New York strawberry

Abstract

Although growing strawberries under low tunnels is increasing in popularity across the northeastern United States, little is known of how they impact the presence of natural enemies and pollinators that provide key ecosystem services on strawberry. We employed passive (fruit collections, sticky cards and pitfall traps) and direct (direct observations, leaf brushing and fruit bagging) monitoring over 2–3 growing seasons to compare the abundance and impact of beneficial insects and mites on strawberry grown under low tunnels versus the open field. Three different low tunnel plastics ranging in UV-selectivity were included to determine any effect of UV exclusion on natural enemy and pollinator presence. Plant yield and fruit marketability was higher under low tunnels compared to the open field for two of three years observed. The abundance of predators, and to a lesser extent parasitoids, was similar or higher under low tunnels compared to the open field. However, catch on sticky cards revealed lower densities of parasitoids under tunnels. There was some evidence that UV-selecting plastics resulted in poorly pollinated fruit compared to UV-transmitting and open-field treatments. However, there was no difference in pollinator presence among treatments, so the mechanisms causing the plastic effect are unclear. Overall, we conclude that growing strawberries under low tunnels, regardless of UV selectively, can support higher and more marketable yield in some years while likely having neutral to positive impacts on beneficial predators, parasitoids and pollinators.