Ground Predator Activity-Density and Predation Rates Are Weakly Supported by Dry-Stack Cow Manure and Wheat Cover Crops in No-Till Maize

Response of Spider and Epigaeic Beetle Assemblages to Overwinter Planting Regimes and Surrounding Landscape Compositions

The rotation patterns of summer rice-winter oil seed rape and summer rice-winter fallow are the main planting regimes in the rice ecosystem in southern China. However, the impact of local rotation patterns and landscape factors on the overwintering conservation of predators in spider and epigaeic beetle assemblages remains poorly understood. Here, we investigate the diversity and density of spiders and beetles over two consecutive winters (2019/2020 and 2020/2021), focusing on the impact of two rotation patterns (rice-fallow and rice-oilseed rape) and surrounding landscape compositions on predator diversity. The main findings of our research were that spiders were more abundant and had a higher activity density in the fallow rice fields (FRs) compared to the oilseed rape fields (OSRs), whereas ground beetles exhibited the opposite pattern. Specifically, fallow rice fields supported small and ballooning spiders (e.g., dominant spider: Ummeliata insecticeps), while OSRs supported larger ground beetles (e.g., dominant beetles: Agonum chalcomus and Pterostichus liodactylus). Moreover, the composition of spider assemblages were impacted by semi-natural habitats (SNHs) during overwintering, while ground beetle assemblages were influenced by overwinter planting patterns. Overall, our results suggest that different planting regimes and preserving semi-natural habitats are a strategic way to enhance species diversity and functional diversity of ground predators. It is, therefore, recommended that to conserve and improve predator diversity during overwintering, land managers and farmers should aim to maintain diverse planting regimes and conserve local semi-natural habitats.

Ground beetles suppress slugs in corn and soybean under conservation agriculture

Conservation agriculture practices such as eliminating tillage and planting high residue cover crops are becoming increasingly important in field crop systems in the US Mid-Atlantic. However, these practices have sometimes been associated with an increase in moderate to severe damage to field crops by slugs. Conserving natural enemy populations is a desirable way to manage slug infestations because remedial control measures are limited. Here, we tested the effects of conservation practices, weather, and natural enemies on slug activity-density measured by tile traps placed among 41 corn and soybean fields during the spring of 2018 and 2019 in the Northern Shenandoah Valley, Virginia, USA. We found that a positive effect of cover crops on slug activity-density was reduced by tillage and that slug activity-density declined with increasing ground beetle activity-density. Slug activity-density also declined with decreasing rainfall and increasing average temperature. Weather was the only significant predictor of ground beetle activity-density, which was reduced in sites and weeks that were relatively hot and dry or that were cool and wet. However, we also found a marginally significant negative effect of pre-plant insecticides on ground beetles. We suggest that the observed interacting effects of cover crops and tillage reflect favorable conditions for slugs provided by increased small grain crop residue that can be mitigated to some extent by even low levels of tillage. More broadly, our study suggests that implementation of practices known to promote recruitment of ground beetles in crop fields can improve natural suppression of slugs in corn and soybean that are being increasingly cultivated according to conservation agriculture practices.

Early-season plant cover supports more effective pest control than insecticide applications

Growing evidence suggests that conservation agricultural practices, like no-till and cover crops, help protect annual crops from insect pests by supporting populations of resident arthropod predators. While adoption of conservation practices is growing, most field crop producers are also using more insecticides, including neonicotinoid seed coatings, as insurance against early-season insect pests. This tactic may disrupt benefits associated with conservation practices by reducing arthropods that contribute to biological control. We investigated the interaction between preventive pest management (PPM) and the conservation practice of cover cropping. We also investigated an alternative pest management approach, integrated pest management (IPM), which responds to insect pest risk, rather than using insecticides prophylactically. In a 3-year corn (Zea mays mays L.)-soy (Glycine max L.) rotation, we measured the response of invertebrate pests and predators to PPM and IPM with and without a cover crop. Using any insecticide provided some small reduction to plant damage in soy, but no yield benefit. In corn, vegetative cover early in the season was key to reducing pest density and damage, likely by increasing the abundance of arthropod predators. Further, PPM in year 1 decreased predation compared to a no-pest-management control. Contrary to our expectation, the IPM strategy, which required just one insecticide application, was more disruptive to the predator community than PPM, likely because the applied pyrethroid was more acutely toxic to a wider range of arthropods than neonicotinoids. Promoting early-season cover was more effective at reducing pest density and damage than either intervention-based strategy. Our results suggest that the best pest management outcomes may occur when biological control is encouraged by planting cover crops and avoiding broad-spectrum insecticides as much as possible. As part of a conservation-based approach to farming, cover crops can promote natural-enemy populations that can help provide biological effective control of insect pest populations.