Balancing row cover pest and pollination management in organic cucurbit production

Balancing pest control and pollination is a dual challenge for pollinator-dependent crops and the producers that grow them. For organic cucurbit production, organic compliant insecticides underperform at suppressing pests and can have nontarget impacts on pollinators. One promising alternative is pest-protective row covers, which successfully exclude insect pests from damaging cucurbit crops. However, they also exclude pollinators. In this study across two years, four row cover pollination management strategies were compared for their efficacy for acorn squash (Cucurbita pepo L.). Row covers were installed at crop transplant and four treatments were initiated: on–off (row cover removed at flowering), on–off–on (row cover removed at flowering and reinstalled post-flowering), open ends (row cover tunnel ends opened at flowering and reclosed post-flowering), and full season (row cover installed through whole season, commercial bumble bee colonies installed at flowering). During the pre-flowering net stage (when row covers were installed), all treatments had low pest abundance and were not statistically different. In the post-flowering net stage, the full season and open ends treatments had statistically lower cucumber beetle pest abundance relative to the on–off–on treatment. The number of seeds per squash fruit weight, an indicator of pollination success, was statistically lower in the full season treatment relative to the on–off–on treatment in 2021, which may be explained by the statistically lower bee activity in the full season treatment relative to the on–off and on–off–on treatments. Squash seeds were not counted in 2020. The open ends treatment had statistically higher marketable yield than the full season and on–off–on treatments in 2020; in 2021, there was no difference in marketable yield across treatments. For the open ends treatment, increased distance from the opened tunnel ends significantly decreased the pest abundance, while it significantly increased marketable yield. However, there was no relationship between pollinator activity and distance to the tunnel opening. This two-year study suggests the open ends strategy had the most consistently high yields, while it reduced pollination management effort and eliminated the costs of commercial bee colonies compared to other treatments. Only minor pressure from insect-vectored diseases was observed during the study, thus, the advantages of each pollination strategy should be considered in relation to varying pest, pollinator, and disease conditions.