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Maintaining habitat throughout the season in annual cropping systems provides resource stability for arthropod communities. Stabilizing resource availability should lead to diverse predatory communities and their associated ecosystem services such as biological control. There is a need for studies to test change in predator communities due to habitat provisioning and estimate associated food web responses. Here we quantified predator community structure and used molecular gut-content analysis to reconstruct predator food webs in response to winter cover crops (i.e. cereal and legume based) in a cotton agroecosystem. Predators were collected from experimental field plots during each major crop development stage in 2017 and 2018, and PCR was used to estimate predator roles and responses to cover crop treatments. Cotton planted into a rye cover crop residue promoted unique predator communities in the early and mid-season as compared to no-cover fields. Correspondingly, we observed dissimilar prey consumption among cover crop treatments. While predators consumed incidental pests at high frequencies (e.g. aphids), predation on key pests by natural enemies in this system was lacking. The use of winter cover crops and reduced tillage practices increased the consumption of alternative prey by natural enemies on seedling cotton, encouraging high predator diversity that aligns temporally with potential early season pest outbreaks. Therefore, cover crops should be further integrated into integrated pest management strategies.

A shift to more ecologically based farming practices would improve the sustainability and economic stability of agricultural systems. Habitat management in and around agricultural fields can provide stable environments that aid in the proliferation of natural enemy communities that moderate pest populations and injury. Winter cover crops offer a potentially cost-effective approach to improving habitat that supports natural enemy communities early in the growing season. We investigated the effects of winter cover crops including cereal rye (Secale cereal L.) and crimson clover (Trifolium incarnatum L.) on the abundance and diversity of natural enemies, key pest populations, biological control services, and cotton yield. Winter cover crops were established on 0.4 ha replicated field plots in the fall of 2017 and 2018. Suction sampling during each cotton development stage demonstrated that a rye cover crop promoted greater abundance and diversity of natural enemy communities in early cotton stages. Extensive leaf sampling of seedling cotton showed that cover crops significantly reduced thrips infestations. Furthermore, stink bug boll injury decreased on plots prepared with a rye cover compared to cotton lacking this additional habitat. Combining end of season yield results and management practices with an economic analysis of the costs of production, the value of cotton grown into a cover crop was cost competitive with conventional (no cover) cotton production. These results suggest that conventional growers utilizing cover crops could reduce insecticide inputs through natural reductions in pest pressure, and overall do not incur additional production costs.

Winter cover crops shape early-season predator communities and trophic interactions.

No abstract