Farmers on the lookout as armyworm reports coming in

As of writing this article, many parts of the state, are in abnormally dry or moderate drought conditions. Given the current stage and conditions of crops, farmers should be vigilant of armyworms.

Before any application of insecticide for armyworms, it is important to scout for economic thresholds. (The economic threshold for small grains is four to five larvae per square foot and/or once larvae begin to clip grain heads. The threshold in whorl stage corn is 25 percent of plants with two larvae per plant or 75 percent of plants with one larvae per plant.) If economic thresholds are not being reached, then the population is likely being kept in check by natural enemies. If that is the case you should hold off on spraying, but continue scouting.

Lush grasses are the preferred sites for egg laying. These can include stands of small grains, cover crops, and grass field borders.

Armyworms seldom feed on broadleaf crops. The risk is increased in fields where a live grass cover crop or grass weeds are present at the time when moths are laying eggs.

Since true armyworms cannot overwinter in Minnesota, they migrate into the state each spring.

The larvae are active at night or on cloudy days. Scout using a sweep net in grassy borders and in small grains. Also, shake the small grain canopy and search the ground for larvae.

Cultural control can be effective for armyworm management. Maintaining good, early season weed control and avoiding late termination of grass cover crops can reduce the attractiveness of fields to egg-laying moths.