Growers should scout pastures, hay fields and winter wheat for armyworm. University of Missouri insect trapping system indicates armyworm moth flights, so armyworm is in the area. It is a matter of where the moths decide to lay eggs at a suitable site then they will hatch and start consuming vegetation.

Scout fields for activity in evenings as they are actively feeding. Scout fields every three to four days. Only sunny days, larvae will be on the ground under plant debris or under soil clods. Brown frass may be found also on plants or on the soil surface.

Always look for parasitized worms as this will indicate the worms are being infected naturally and will control the pest for you. If many worms are parasitized, avoid using insecticides.

To determine treatment, count larvae in five places for each 50 acres of field size. Each counting site should be a square of 3 feet by 3 feet.

The threshold for insecticide treatment is an average of four larva per square foot. Ignore larvae larger than one inch because they will soon stop feeding and pupate.

As far as wheat, armyworm is very destructive because of head clipping. An application should be made if two percent of heads are clipped and larvae are present.

For more information, contact Wayne Flanary, Field Specialist in Agronomy, University of Missouri at 816-279-1691.