Linda Geist

LAMAR, Mo. – Now is the time to scout for fall armyworms in pastures and hayfields, says University of Missouri Extension entomologist Kevin Rice.

Agronomists in southeastern Missouri and northern Arkansas report sightings of fall armyworm in grass and legume crops, says Jill Scheidt, MU Extension agronomy specialist.

Fall armyworms do not overwinter in Missouri and migrate northward from Gulf Coast states. They damage forages by eating through the tender top leaf layer and leaving holes, says Rice. Infested fields may appear drought-damaged.

Armyworms march quickly into lush, green pastures and fields, so regular scouting is necessary. They feed on hundreds of host plant species, including tall fescue and alfalfa.

Fall armyworm does not feed during the heat of the day, so scout in early morning or evening. Look for bird or other predator activity, which is an indicator of infestation.

To scout for fall armyworm, select 10 random locations in a field and look for larvae in a 1-square-foot area at each location. If you find three or more half-inch larvae per square foot, consider chemical control or early harvest. Larvae more than 1.5 inches long are close to pupation, so chemical control may not be warranted.

Fall armyworms resistant to pyrethroids were discovered in Arkansas, says Rice. If chemical control is warranted, use a different chemical class to manage fall armyworm.

Follow all label precautions and restrictions. Contact your local MU Extension agronomist for more information.

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