Department of Plant and Environmental Sciences, Clemson University, Clemson, SC.
Department of Forest and Wildlife Ecology, University of Wisconsin, Madison, WI.
Environ Entomol. 2021 Apr 23;50(2):330-336. doi: 10.1093/ee/nvaa168.
Weed management requires enormous labor investments from vegetable farmers, yet crops vary in how much weed pressure they can tolerate without yield loss. Moreover, until weeds reach a point where they threaten yield or approach seed production, they can increase biodiversity and provision food and habitat to attract predatory insects. In two related field experiments, we quantified impacts of weed presence and diversity on pests, predators, and biocontrol of both weed seeds and insect prey. We also measured yields of two vegetables that vary in competitiveness (eggplants and turnips) across two weed management treatments (weedy and weed-free), to determine productivity costs of tolerating weeds. Allowing weeds to grow adjacent to rows of eggplants increased abundances of predators and reduced pests. Surprisingly, relaxing weed management came at no cost to eggplant yield. In contrast, tolerating weeds in turnips had strong yield costs, and did not benefit predators or decrease pest pressure. On both crops, pests declined as weed diversity increased. Yet, weed treatments had no impact on consumption of weed seeds or sentinel prey by soil-surface insects, which were dominated by red imported fire ants. Our results suggest that highly competitive crops might benefit from stronger natural pest control when weeds are less-aggressively managed. However, herbivores and predators had unique responses to weeds that were crop-specific. To help farmers allocate limited weed management labor resources, future work should examine the relative competitiveness of a wider variety of vegetables over a gradient of weed pressure while measuring corresponding impacts on pest control.
杂草管理需要蔬菜种植者投入大量劳动力，但不同作物对杂草的耐受能力不同，在不降低产量的情况下，杂草的压力水平也不同。此外，直到杂草达到威胁产量或接近种子生产的程度之前，它们可以增加生物多样性，并提供食物和栖息地，以吸引捕食性昆虫。在两项相关的田间试验中，我们量化了杂草的存在和多样性对害虫、捕食者以及杂草种子和昆虫猎物的生物防治的影响。我们还测量了两种竞争力不同的蔬菜（茄子和萝卜）在两种杂草管理处理（杂草丛生和无杂草）下的产量，以确定容忍杂草的生产力成本。允许杂草在茄子行旁生长会增加捕食者的数量并减少害虫。令人惊讶的是，放松杂草管理对茄子的产量没有影响。相比之下，容忍萝卜中的杂草会产生强烈的产量成本，并且不会使捕食者受益或减少害虫压力。在这两种作物上，害虫的数量随着杂草多样性的增加而减少。然而，杂草处理对土壤表面昆虫对杂草种子或哨兵猎物的消耗没有影响，这些昆虫主要是红火蚁。我们的研究结果表明，当杂草管理不那么积极时，高竞争力的作物可能会受益于更强的自然害虫控制。然而，食草动物和捕食者对杂草的反应具有独特性，具体取决于作物。为了帮助农民分配有限的杂草管理劳动力资源，未来的工作应该在测量对害虫控制的相应影响的同时，研究更广泛的蔬菜在杂草压力梯度上的相对竞争力。
