Impact of the Timing and Use of an Insecticide on Arthropods in Cover-Crop-Corn Systems

SIMPLE SUMMARY: Cover crop use is increasing in the USA as a sustainable method. However, cover-crop pests can migrate to the following cash crop, threatening its productivity. As a preventative strategy to minimize pest transitions, growers may apply insecticides at the cover-crop termination time. Our study aims to better understand the impact of insecticide application as a preventive strategy against arthropods, either at cover-crop termination or when the cover crop is decomposing. Our finding indicates that preventive insecticide applications are not needed, highlighting the importance of scouting for pests before making a management decision. Moreover, we hypothesize that cover-crop biomass might create a physical barrier protecting arthropods below the cover-crop canopy. ABSTRACT: Cover crops provide a habitat for pests and beneficial arthropods. Unexpected pest pressure in a cover-crop-to-corn system can occur and result in increased use of insecticides. Eight site-years of on-farm field studies were conducted in 2019, 2020, and 2021. The objective of the study was to evaluate the impact of insecticide timing relative to cover-crop termination on arthropod activity in a cover-crop-to-corn system. The treatments consisted of (i) glyphosate to terminate the cover crop, (ii) glyphosate and pyrethroid tank mix to terminate the cover crop, and (iii) glyphosate to terminate the cover crop and pyrethroid application 25 days after the termination. Arthropod activity was measured with pitfall traps before and at each treatment application. A total of 33,316 arthropods were collected. Total arthropods, Collembola, and Aphididae were the only taxa reduced with an insecticide application. The other arthropod taxa were mainly influenced by the sampling period. No significant pest pressure occurred at any site-year. Insecticide applications are not generally needed in a cover-crop-to-corn system. Scouting for pests and applying strategies only when necessary is crucial to conserve potentially beneficial arthropods in the system.