Integrated Weed Management in Cucurbit Production Using Spring-seeded Grass Cover Crops

Achieving commercially acceptable weed control in plasticulture vegetable production systems can be challenging because many herbicides do no provide season-long control. Additionally, several weed species have recently evolved resistance to labeled herbicides. Consequently, multiple cultivations or frequent hand-weeding are needed to control emerged weeds. Cover crops have recently gained attention as a tool for helping to manage weeds. Field studies were conducted in Maryland and New Jersey to assess the efficacy of combining spring-seeded grass cover crops and herbicide treatments for weed control in cucumber and watermelon production. Three spring cover crop treatments consisting of cereal rye, spring oats, or cereal rye and spring oats were hand-broadcasted after laying plastic in Apr 2021 and 2022. Postplant treatments were applied to cover crops and emerged weeds 78 days later, ∼3 weeks after planting each crop. Postplant treatments included shielded herbicide applications (paraquat or clethodim) or crimping without an herbicide. Residual herbicide (fomesafen + S- metolachlor) was included or not with each postplant treatment. Cover crops decreased broadleaf weed density before and 2 weeks after postplant treatment (WAT) by 73% and 68%, respectively, and weed biomass 6 WAT by 84% compared with no cover. Terminating an oat cover crop with paraquat totally suppressed smooth pigweed 2 WAT compared with clethodim or crimping treatments. Overall, cover crop treatments showed 50% greater weed control compared with no cover. Weed control in the interrow area ranged from 90% to 95% when paraquat was applied to a cover crop compared with less than 75% following crimping a cover crop. Cucumber and watermelon commercial yield decreased 63% and 52%, respectively, when cover crops were not used. These results show that spring-seeded cereal cover crops can be successfully integrated with an herbicide strategy to provide effective weed control in cucurbit production.