Department of Plant and Environmental Sciences, Coastal Research and Education Center, Clemson University, Charleston, SC.
USDA-ARS, Temperate Tree Fruit and Vegetable Crop Research Unit, Wapato, WA.
Environ Entomol. 2020 Dec 14;49(6):1327-1334. doi: 10.1093/ee/nvaa105.
Organic vegetable farmers rely heavily on labor-intensive tillage for weed management, which adversely affects soil health and harms beneficial insects that consume crop pests and weed seeds. Using cover crop residues as a weed-suppressive mulch enables some reduction in tillage, and combining this tool with recently developed organic herbicides may further enhance weed suppression in vegetable production. However, organic herbicides may also adversely affect beneficial insects, and their nontarget effects are unknown. Here, we examine the combined impacts of cultural and chemical tools on weed cover while monitoring activity of beneficial epigeal insects and measuring rates of weed seed biological control to assess potential nontarget effects of organic herbicides. In a 2-yr experiment, we compared three cover crop mulch treatments and three organic herbicide treatments (capric/caprylic acid, corn gluten meal, and herbicide-free) in a reduced-tillage system. Organic herbicides led to no reductions in beneficial insect activity nor weed seed biocontrol. In both years, capric/caprylic acid herbicide and cover crop mulches reduced weed pressure relative to a fallow control treatment, whereas corn gluten meal had no effect. In year 2, a combination of cover crop mulch with organic herbicide had the greatest weed suppression relative to the fallow control. Integrated weed management is a perpetual challenge, but our results suggest that organic herbicides used in concert with cover crop mulch may enhance weed control and reduce the need for tillage, with limited collateral damage to natural enemies.
有机蔬菜种植者严重依赖劳动密集型耕作来管理杂草，这会对土壤健康造成不利影响，并伤害消耗作物害虫和杂草种子的有益昆虫。利用覆盖作物残茬作为抑制杂草的覆盖物，可以减少一些耕作，而将这种工具与最近开发的有机除草剂结合使用，可能会进一步增强蔬菜生产中的杂草抑制作用。然而，有机除草剂也可能对有益昆虫产生不利影响，其非靶标效应尚不清楚。在这里，我们在监测有益地面昆虫活动和测量杂草种子生物防治率的同时，研究了文化和化学工具对杂草覆盖的综合影响，以评估有机除草剂的潜在非靶标效应。在一项为期 2 年的实验中，我们在减少耕作系统中比较了三种覆盖作物覆盖物处理和三种有机除草剂处理（辛酸/癸酸、玉米蛋白粉和无除草剂）。有机除草剂并没有降低有益昆虫的活动或杂草种子的生物防治。在两年中，辛酸/癸酸除草剂和覆盖作物覆盖物都降低了相对于休耕对照处理的杂草压力，而玉米蛋白粉则没有效果。在第二年，与休耕对照相比，覆盖作物与有机除草剂的组合具有最大的杂草抑制作用。综合杂草管理是一个永恒的挑战，但我们的结果表明，与休耕对照相比，有机除草剂与覆盖作物覆盖物结合使用可能会增强杂草控制，减少耕作需求，对天敌的附带损害有限。
