On Jan. 18, 2023, Bruce Potter, University of Minnesota Extension IPM specialist, and Dr. Anthony Hanson, UMN Extension IPM educator joined UMN Extension crops educator Ryan Miller for a wide-ranging discussion of European corn borer. This was the second episode of the 2023 Strategic Farming: Let’s talk crops! webinars in this series. 

Questions submitted in advance by people registering for the 2023 Strategic Farming: Let’s Talk Crops! sessions indicated that several were interested in learning more about how adding a cover crop to the larger cropping system can impact insect pests in the cash crop. 

True armyworms (TAW) were an issue for some people’s cash crops in 2022 that had seeded a rye cover crop in fall 2021. Like other migratory pests that are unable to survive the tough Minnesota winter, armyworm moths travel north with weather systems each spring from where they spend their winters in the southern U.S. It is difficult to predict where TAW moths will drop out of the storms that bring them north. According to Potter, “armyworms are attracted to rye, and the denser and taller the better.” The larvae feed on live grasses.  “If moths lay their eggs on a rye cover crop, the resulting larvae will look for another grass plant to feed on when the rye is terminated,” according to Hanson. Although soybeans are as likely to suffer significant armyworm feeding injury, corn crops grown in fields with a rye cover crop are at particular risk. Corn fields with heavy grass weed pressure is also vulnerable.

While rare in Minnesota, fall armyworms arrive later in the growing season than TAW and can lay their eggs in a newly planted rye cover crop, injuring seedlings and both armyworm species can move into corn from lodged grasses in field borders.

“You are adding a little bit more variability and less predictability to the system. You can manage these things, but it is going to require some scouting,” says Potter. Timely termination of your rye cover crop and scouting your cash crop for armyworm feeding injury and larvae are two important practices for managing armyworms. 

For those that missed this session, it is now available to view on YouTube at https://youtu.be/_R9Hbb7M5lA. For more information and to register to attend other weekly session through the end of March, visit z.umn.edu/strategic-farming.