Brassica crops are susceptible to a variety of insect pests of particular significance in organic production systems, including flea beetles, aphids, and lepidopteran caterpillar pests. These pests are abundant on brassicaceous vegetable crops throughout the U.S. and populations frequently are high enough to significantly reduce crop quality. There is an increased interest among small and mid-size vegetable growers to adopt poly-covered tunnels to protect high value horticultural crops. Tunnel production allows for season extension, can protect crops from adverse weather conditions, improve the quality of horticultural crops, and may also influence plant-insect dynamics. Photoselective poly coverings influence light wavelength and transmission in tunnel environments and may affect plant physiological responses as well as incidence of disease and herbivory by insect pests. Here, we explored the impact of UV light blocking and UV light transmitting poly coverings on Lacinato kale (Brassica oleracea var. acephala) production and the effects on pest and beneficial insect populations in a tunnel environment compared to an open field system on certified organic land in Morris, MN. Our results showed that total kale harvestable yield was similar between the poly covered tunnels and open field plot treatments. No differences in yield or insect pest pressure were observed between UV light blocking or transmitting poly covered tunnels but were observed between tunnels and the open field environment. Imported cabbageworm populations were 75% higher in tunnels versus open field plots (P=.0023), however the inverse was observed for cabbage loopers, which were 60% higher in open field plots (P=.0072). No flea beetles were found in tunnels, and an average of 1 beetle/plant was observed in open field plots. Diamond back moth and aphid populations were not different between the tunnel and the open field plots. Overall, insect pest populations did not reach economically damaging thresholds during the study period, likely due to the field plot location which did not have a history of brassica production. Our results showed that light transmission and ambient air temperatures were similar under the photoselective poly coverings. We observed that pest pressure increases rapidly in tunnel environments as the season progressed regardless of poly covering. Although our study did not observe differences in the yield or quality of kale across production systems, there were differences in insect pest populations across systems, indicating a different management approach may be needed to prevent crop damage in tunnel environments.
