Reports of fall armyworms are emerging from Arkansas this week. While populations remain low, larvae have been found in rice and soybean fields with significant grass weed infestations. To date, no armyworms have been reported in Tennessee, but late July is historically when populations begin to appear.

The reported infestations are the grass strain of fall armyworm, which preferentially feeds on grasses such as rice, pastures, and grass weeds. They do not typically infest soybeans, cotton, or corn. Most crop injury occurs after a graminicide is applied to control grass escapes, forcing armyworms into nearby soybeans as the grasses senesce.

Not every field with grass escapes will contain armyworms, and growers who control grass weeds early may avoid the need for an insecticide application later. To date, no pyrethroid control failures have been reported. Growers should scout fields with grass escapes before making herbicide applications. If armyworms are present, consider tank-mixing a full labeled rate of a pyrethroid (e.g., lambda-cyhalothrin or bifenthrin) with the herbicide. If armyworms or other economically important insect pests are not present, an insecticide application is not warranted.