Weeds Impose Unique Outcomes for Pests, Natural Enemies, and Yield in Two Vegetable Crops

Abstract

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.

Phytotoxic Effects of Selected Herbal Extracts on the Germination, Growth and Metabolism of Mustard and Oilseed Rape

“…Additionally, they can cause enormous financial losses [2][3][4]. Weeds can be also the secondary hosts for some pests [5][6][7]. Therefore, synthetic herbicides are widely used to control weeds.…”

“…Using allelopathy to control weeds also includes using allelopathic crop residues [18], cover crops [19], crop rotation [20], and catch crops [21], as well as selecting the allelopathic crop cultivars [22] and new herbicides that are derived from allelopathic chemicals [23]. Allelopathic compounds according to their different structures and properties can be classified into 10 categories: (1) straight chain alcohols, water-soluble organic acids, ketones and aliphatic aldehydes; (2) simple lactones; (3) polyacetylenes and long-chain fatty acids; (4) quinines (anthraquinones, benzoquinones, and complex quinines); (5) cinnamic acid and its derivatives; (6) phenolics (caffeic acid, coumaric acid, vanillic acid, syringic acid, ferulic acid); (7) coumarins; (8) tannins; (9) flavonoids; (10) terpenoids and steroids [24]. They could help to reduce the use of synthetic herbicides, which would lead to less pollution and safer agricultural products [25,26].…”

Effect of summer cover crops on cabbage yield, weed suppression, and N mineralization in a low input cropping system

“…This potential for high weed pressure following a poor SCC stand should be taken into account when planning for the cash crop to follow, as the success of the crop could be greatly influenced. For instance, a poorly competitive cash crop grown following a low biomass producing SCC could translate to increased competition from weeds in the cash crop (Madden et al, 2021).…”

Composition and diversity patterns of weeds in herbicide tolerant maize fields and margins in the Eastern Cape, South Africa

“…Some weeds can be important for various ecosystem services in agricultural lands, such as providing habitat and supporting prey species for higher trophic levels (Ramesh et al 2017). However, in agricultural systems, weeds have been shown to compete with most crops for resources, causing reductions in harvest yields (Madden et al 2021). Weeds compete for water, sunlight, and nutrients that are essential for crop growth and productivity.…”

“…Weeds compete for water, sunlight, and nutrients that are essential for crop growth and productivity. Consequently, weed control and eradication remain necessary within agricultural systems to ensure optimum crop yield (Madden et al 2021).…”