High numbers of armyworms were observed defoliating more than 50 percent of the flag leaf in wheat near Argusville in Cass County. Armyworm outbreaks in North Dakota can occur when large migrations of moths from Southern states occur in early summer.
Moths prefer to lay eggs in moist, shady areas where small grains or grasses have lodged or been damaged by hail or wind. Armyworms feed at night and hide under vegetation or in loose soil during the day. To scout for armyworms in grains, part the plants and inspect the soil for fecal pellets. If pellets or feeding damage is found, look for larvae under plant trash, soil clods or in soil cracks.
The action threshold for armyworms in wheat is when 4 to 5 worms per square foot are present. A listing of insecticides registered for armyworm control in small grains is available from the ND Field Crop Insect Management Guide 2011, E-1143, NDSU Extension Service.