True armyworm in wheat field Photos by Greg Luce, MU Extension
SCOUT FIELDS: True armyworm is showing up in Missouri wheat fields. Agronomists suggest scouting early for these pests as cold, wet weather reduced the predator population for this bug.

How to identify true armyworms in your crop field

Lack of predators this season is leading to an increase in armyworms.

The University of Missouri Extension reports true armyworms showing up in parts of central, west-central and northwestern portions of the state.

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.

True armyworm damages crops and feeds on the foliage of corn, wheat, fescue and other grass plants.

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 says. "Growers should definitely be scouting fields."

"Growers need to be prepared to take action," says 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.

Greg Luce, MU Extension


True armyworm

What to look for

True armyworm overwinters in Missouri as a partially grown larva. Here are a few identifiers of a true armyworm:

• greenish-brown color with a narrow, mid-dorsal stripe
• orange stripes outlined in white along each side of the body
• yellow honeycombed head with 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 depending on crop. Growers can find more information in the free MU Extension guide "Management of the Armyworm Complex in Missouri Field Crops,"  .

For up-to-the-minute information on the armyworm, go to MU Integrated Pest Management's true armyworm page.

Source: MU Extension

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