Hot, dry weather may be a contributing factor, he said. Obermeyer visited Knox County Tuesday and witnessed the damage firsthand. One farmer told Obermeyer armyworm larvae destroyed his pasture, then began feasting on his adjoining lawn. I also observed them eating soybeans. Armyworm larvae range in size from one-fourth inch to 1.25 inches long.
Damage usually appears insignificant when the larva hatches.
When armyworms consume all available green leaf material in a field, they'll move into adjacent fields. The feeding frenzy ends when the larva buries itself in the soil to pupate. In late summer the adult moth emerges and begins laying eggs. Several pesticides are available for treatment, but one needs to be aware of harvest restrictions on the product label. For example, with pastures you can spray with malathion while the cattle continue grazing, while with Sevin-brand pesticide you must remove the animals for two weeks.