By Linda Geist
True armyworm are showing up in parts of central, west-central and northwestern Missouri.
University of Missouri Extension agronomists reported at a weekly teleconference that the pest is present in several counties. True armyworm damages crops and feeds on the foliage of corn, wheat, fescue and other grass plants.
This year’s cold, wet planting season laid the groundwork for armyworm to cause feeding damage. These conditions slow the reproduction of armyworm’s natural enemies. Infestations appear worst in late-planted, no-till fields, especially in dense wheat and grass fields.
MU Extension agronomist Greg Luce says that numbers are not cause for alarm in most areas. “However, we have some very high reports from northwest Missouri and portions of western and central Missouri,” he said. “Growers should definitely be scouting fields.”
“Growers need to be prepared to take action,” said Wayne Flanary, MU Extension agronomist in Holt County. Travis Harper, agronomy specialist in Henry County, reported that growers see armyworms in fescue fields near Kansas City.
True armyworm overwinters in Missouri as a partly grown larva. They are greenish brown with a narrow, mid-dorsal stripe. Orange stripes outlined in white run along each side of the body. The yellow honeycombed head features dark lines. Larvae are nocturnal feeders that hide in the leaf whorl during the day. They also hide in soil cracks and beneath surface litter.
Two or three generations of armyworm grow in Missouri each year. The first generation of May and June causes the most crop damage.
Scouting saves money and reduces insecticide use. Scouting methods vary for crops. Growers can find more information in the free MU Extension guide “Management of the Armyworm Complex in Missouri Field Crops” at extension.missouri.edu/p/g7115.