Field Check: Cutworms in Soybeans Planted Green into Cover Crop

“I heard from a customer the other day about cutworms in a soybean field that was planted green into cereal rye. I was wondering if this is common and do we need to recommend scouting for cutworms or other pests when using cover crops?” - Chris Prochnow, Territory Manager for Agassiz Seed and Supply

Dr. Janet Knodel, an extension entomologist at North Dakota State University, joins us to help answer Chris’s question. North Dakota is home to at least 32 different species of cutworms.

“Most (cutworms) do love weedy fields or grassy fields in the fall. So that’s probably why they ended up in the rye field is because it was seeded in the fall and that’s very attractive to most of the species of cutworms. And then they cause damage in the spring.” Dr. Janet Knodel

Eggs are laid in the soil usually in September. Some species will stay as eggs over winter and some will hatch into larvae. The larvae or caterpillar is the damaging stage. When scouting, look for evidence of defoliation, bare spots or cut plants laying on the ground. Some species will clip the plant when it's young and some will climb them and damage the leaves. The larvae and adult moth are active at night so they may not be readily apparent during the day.

“You pretty much just need to get out in the spring and scout and monitor the fields for infestation.” - Dr. Janet Knodel

Four or more larvae per foot of row is the threshold for wheat, barley, oats and rye. You want to “implement your chemical controls” when they are smaller larvae. Towards the end of their feeding schedule, typically at the end of June, the larvae become more difficult to kill as they are more mature. Unfortunately there aren’t any “forecasting models” for cutworm infestation. This makes it hard to predict which field they will infest and what environments they prefer. Dr. Knodel explains this is why regular scouting is critical to managing any potential infestation..

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Soil Sense Podcast is hosted by Tim Hammerich of the Future of Agriculture Podcast.