Tips for managing insecticides and cover crops in corn
Although wheat stem maggot has been a concern for some Nebraska farmers who plant corn directly into a growing cover crop, entomologists at the University of Nebraska-Lincoln want farmers to scout their fields before adding an insecticide to the herbicide during cover crop termination.
With support from an $11,716 SARE Graduate Student grant, farmers Dave Nielsen and Ron Sladky were able to work with UNL graduate student Gabriela Inveninato Carmona to develop sustainable management strategies for their cover crop and corn systems. Nielsen and Sladky wanted to minimize pests while maximizing beneficial arthropods on their farms.
“The most common question is in regard to tank mixing an insecticide with a herbicide at the time the cover crop is terminated,” said Carmona in a 2018 CropWatch report. “We do not recommend this practice for two reasons. First, an insecticide application without any knowledge of pest presence will likely kill beneficial insects in the cover crop that may provide a benefit to the subsequent cash crop. We encourage ag professionals to scout cover crops for wheat stem maggot adults or larvae prior to termination to assess pest pressure,” she said. “If farmers or consultants find high numbers of wheat stem maggots in their cover crop, we would suggest terminating the cover crop at least 14 days prior to planting corn. If such practices are not possible, producers should consider making an insecticide application 11 days after a glyphosate application.”
Ultimately, the project demonstrated the value of scouting as part of a pest management strategy. Carmona’s faculty adviser on the project, Justin McMechan, recently received an additional grant to keep working on the topic. The $39,906 SARE Partnership grant increases the study’s size to four farmers, but still includes Nielsen and Sladky, the two farmers who contributed to Carmona’s research project.
“Having the opportunity to work with growers and better understand the challenges they are facing when using cover crops has had a significant impact on my professional development and confidence as a scientist,” said Carmona, who is now pursuing a Ph.D. at UNL. “We want to keep working closely with growers to reduce their reliance on pesticides and move towards a more integrated pest management strategy.”