Written by Jenny Brhel, Nebraska Extension Educator
Fall armyworms marched across one of our paddocks that were grazed last month in spite of leaving half the grass. Notice to the line they didn’t impact the stockpiled grass paddocks in the foreground of the pic. I keep seeing this-that they seem to prefer new growth-so be watching any green crops and lawns you have with newer growth. They have taken out roadside ditches, though, to move across the road.
Fall Armyworms have been around for about 5 weeks now. They’ve really ramped up feeding in pastures, alfalfa, and lawns. Watch fields recently grazed, alfalfa which was recently hayed, and any small grains/cover crops that you are seeding now. Threshold is 3-4 armyworms per square foot but most situations have more. They feed at night and the larger larvae can take out pastures within a day or two. More information at: https://go.unl.edu/oex0.
Using cover crops to reduce other input costs: With an earlier harvest season upon us, tight economics, increasing input costs, and weed resistance issues, the following are considerations for using cover crops to offset and/or reduce other input costs. These considerations come from walking alongside growers who are currently using these practices in their operations at scale and also from research. While adding a cover crop is an additional input cost, look through what I propose below and pencil out the economics for yourself on your own operation. Even if you just try something on one field, it’s worth giving it a try for any of the goals mentioned below.
Forages: Converting some crop ground to annual forages for grazing makes a great deal of economic sense, particularly if you own cattle and crop ground. I will write a separate article on this. For now, rye, triticale, and hairy vetch are options to be considering for spring forage grazing that can be planted yet this fall.
If Planting Soybeans: Goals that fit this consideration: erosion control, weed and disease management. Planting rye this fall or oats in March followed by planting soybeans green into the small grain helps in several ways. First, you can reduce a full PRE-herbicide and only apply the glyphosate at termination time with a residual product if it gets rained or watered in. You should only need 1 POST-herbicide application with a residual product. We have seen rye reduce impacts to soybeans from hail and off-target dicamba. We have seen rye result in no need for a fungicide application for white mold. We have seen oats and rye reduce soybean cyst nematode numbers in fields and reduce sudden death syndrome in fields. There is plenty of research proving how small grains reduce palmer and also soybean diseases.
- For consideration, pencil out removing: Full PRE-herbicide, Second POST-herbicide. With scouting, you can also pencil out removing: Fungicide for white mold. This works best if you plant the soybeans green into the small grain and wait to terminate till closer to flag leaf/boot stage of the small grain.
If Planting Corn: Goals that fit this consideration are: erosion control, weed management, nitrogen from legumes, reducing nitrogen leaching, grazing prior to corn planting. Plant rye, wheat, or winter barley this fall with hairy vetch. Corn can be either planted green into the small grain/vetch mix or the small grain can be terminated pre-plant by glyphosate or clethodim. Don’t use a regular PRE herbicide and allow the vetch to grow till you apply your POST-herbicide that includes an HPPD inhibitor (Callisto-type chemistry to kill the vetch). The vetch will provide nitrogen for the corn crop and an incredible mat for weed control. If one delays corn planting till May 5-15 time-frame, there’s also opportunity to graze the small grain/vetch mix prior to small grain termination and corn planting. While the growers I’ve worked with haven’t observed toxicity from grazing hairy vetch, there are some concerns with this: https://eupdate.agronomy.ksu.edu/article_new/grazing-cover-crops-toxicity-considerations-320.
What one does really depends on the goals. Some are choosing to plant hairy vetch without a small grain to supplement nitrogen. In that case, one needs at least 15 lb/ac vetch seeded preferably in September. If allowed to grow till at least May 10-15 in our area, hairy vetch can provide 50-100 lb nitrogen per acre that we can credit…depending on seeding rate, when it was planted and terminated. Taking a biomass sample next spring will help you determine what potential you have. I highly recommending coupling this with using technology like Sentinel Ag to show when the nitrogen is released to the crop. We had 3 on-farm research studies where corn was planted after hairy vetch in 2025. We don’t have yield results yet, but we did see all three studies show nitrogen release from the vetch around July 2nd. It’s incredible to use tools like this to watch mineralization (or lack of) occur year by year as we just don’t know how to tell this otherwise. Please reach out to me if you’d like to talk through scenarios that may fit your farm goals.
