Strategic Farming Field Notes: Small grains updates and cover crop termination information

By Claire LaCanne, Ryan Miller, and Liz Stahl, Extension Educators – Crops and Jochum Weirsma, Extension Small Grains Specialist

Extension Small Grains Specialist, Dr. Jochum Weirsma, provided a small grains overview and progress update and Ryan Miller, Extension Educator – Crops, discussed cover crop termination during the May 27 Strategic Farming: Field Notes session. They were joined by moderator Liz Stahl, Extension Educator – Crops.

Small grains updates

The first wave of small-grain fields, planted primarily across southern Minnesota, went in during the last couple of days of March. There was then a bout of cold weather about 5-7 days after planting, and even though that was concerning, those fields did not seem to have any issues from the cold snap. Trial plots that Jochum seeded currently have excellent stands despite the cold snap, even where temperatures dipped to 12° F in Becker, MN.

Now, those temperatures don’t reflect soil temperatures, but this demonstrates that small grains are relatively robust when it comes to handling adverse conditions right after planting. Planting was halted a few times in southern Minnesota but overall, stands are looking good at this point. Winter rye is fully headed or starting to head across southern Minnesota.

In northern Minnesota, it’s been relatively dry, and there have been some significant wind erosion events resulting in some small grains being sandblasted. These fields should recover with ultimately minimal damage and normal tillering. Currently, small grains are reaching the third to fourth-leaf stage in northern Minnesota, and weed control is underway. Historically, growth regulator herbicides have been the preferred choice for weed control in small grains, but be cautious of the risk of injury, especially with high temperatures in the forecast.

In relation to weather, rye is a cross-pollinator, and pollen sterility can occur at or above 95° F. Jochum has not seen that happen in Minnesota to date. However, sterility can also occur when temperatures dip down below 32° F. Pollen sterility can definitely impact yield.

Overall, it’s been too cool and is still too early to see many of the diseases we worry about for small grains. We also haven’t heard of insect issues just yet.

University of Minnesota Extension has been conducting small grains insect and disease field scouting in western Minnesota for about 15 years now, in collaboration with North Dakota State University and funded by the Minnesota Wheat Research and Promotion Council to inform producers and the research community of the presence of disease and pests. Please complete this form if you would like to volunteer a field to contribute to these maps and receive pest data.

Cover crops in southern Minnesota

Cover crop research plots in the Rochester area were planted in the fall and conditions were and remained dry, resulting in variable establishment. Winter cereal rye was drilled at 60 lbs/acre fairly late after corn harvest, and then didn’t germinate in the fall. The seed remained dormant in the soil until spring and then germinated, which reflects how difficult it can be to get good establishment later in the season. Corn silage provides a longer window for cover crop establishment because it’s harvested earlier in the season and would likely allow more time for the cover crop to catch some rainfall and germinate in the fall.

As context, the weather has been a challenge so far this year because of cool spring temperatures and abnormally dry conditions. These two factors, especially together, can result in poor herbicide activity. Some folks terminated their cover crops early because of the moisture challenges, but the cool, dry conditions have resulted in less than ideal termination in some instances.

Cover crop research trial

In this research trial, various herbicide combinations are being tested for their effectiveness on cover crop termination and their impact on weed control. In addition, cover crop termination timing is being evaluated for its impact on the amount of weed suppression provided by the cover crop and interactions with herbicide performance. Three termination timings are being examined; 10 days before planting, at planting, and 10 days after planting. Treatments prior to planting and at planting can include some group 14 burndown herbicides that cannot be used 10 days after planting. A new product from Valent containing Rapidicil technology was included in the early and at-planting burndown timings. Herbicides containing the Rapidicil technology are pending Environmental Protection Agency (EPA) and then state registrations.

Preliminary findings so far indicate that the Rapidicil technology worked quickly and was nearing 100% termination of cereal rye at seven days after application, even with cold and dry conditions. Another note regarding termination is that control gets a little less consistent into the boot stage of cereal rye. As cereal rye starts to head out, it becomes more challenging to get good termination of the cereal rye cover crop. Stay tuned to see how these work and how the trials play out.

Photo 1 - Winter cereal rye planted in the fall of 2024 and terminated at planting in Waseca in 2025. Photo credit: Liz Stahl, University of Minnesota Extension. 

Other cover crop considerations

Outside of the herbicide and weed world, another concern with cover crops in southern Minnesota is the increased risk of insect pests. Cover crops can attract migrating insects when they blow in from the south. An example of this is true armyworm, which has the potential to be a very destructive crop pest in the southern part of the state. Luckily, true armyworm numbers have been low this year, as captured in the University of Minnesota trapping network. The trapping network is helpful in monitoring the presence of these more sporadic insect pests.