Cover crops can attract both pest and beneficial arthropods. Damage from insect pests is based on a number of different factors such as, timing of cover crop establishment or termination method, number of years with a cover crop, weather conditions, and the interval between termination and planting as well as the subsequent cash crop species. Studies and field observations have shown significant risks from pests such as black cutworm, wireworm, Japanese beetle, green cloverworm, southern corn rootworm, seed corn maggot, stinkbugs, and bean leaf beetle and slugs with rye cover crops (Smith et al. 1988). In contrast, Koch et al. 2012 reported reduced aphid and bean leaf beetle population with a rye cover crop. Methods of termination varied considerably between studies (plowing, paraquat, or mowing). In addition, termination dates were not utilized in a way to evaluate their impact on insect populations. Such studies have demonstrated the risk with each of these pests, but no studies have been conducted to determine how management practices such as the timing of termination might influence this relationship.

- Evaluate how the timing of termination of cover crop influences the potential for insect damage and/or
weed suppression in the subsequent soybean crop.
- Determine the impact of cover crop termination on soybean biomass taken at early vegetative stages of
soybean development.

Cover crops can increase soil organic matter, soil tilth, water infiltration, nutrient capture, weed control and reduce soil erosion. Despite these benefits, farmers face significant challenges with spring termination of cover crops. In 2017, a cold wet spring reduced herbicide efficacy for terminating wheat and rye cover crops resulting in “green planting” of both corn and soybeans as the cover crop was still alive. NRCS Nebraska
guidelines indicate that cover crops should terminated at or prior planting a cash crop depending on their location within the state. No studies have been conducted to evaluate the risk or benefits of termination timing relative to soybean planting on insects or weeds. This 3-yr project would assess the timing of termination of wheat or rye cover crops relative to soybean planting on farmer fields across eastern and central Nebraska. Sites would consist of an existing rye or wheat cover crop terminated with glyphosate using a backpack sprayer at three different times during the spring prior to and after soybean planting. Soybean fields will be evaluated twice during the early vegetative stage and once during the reproductive stage for insects, plant damage, and yield will be recorded on plots. Weed suppression potential of cover crop will be evaluated at termination and just prior to soybean canopy closure. Findings will be disseminated through field days, conferences, CropWatch articles, as well as extension and research publications. Results from this study would assist farmers to make an informed decision on timing of termination of cover crops leading to reduced risk, increased yields and adoption of cover crop systems.

Updated May 19, 2023:

View uploaded report

The results from this project would provide farmers with an estimation of the risk and management potential for terminating a cover crop (wheat or rye) relative to soybean planting. Such information is critical for identifying newly emerging pests of cover crop systems as well as existing pest issue potentials. In addition, farmers will have an understanding of how such practices might influence weed suppression from a cover crop depending on the termination date. Such practices may also inform NRCS guidelines for termination of cover crops and provide critical information for crop insurance and cover crop guidelines.