Much of the armyworm damage has occurred in counties that have pastureland. There are several resources at the University of Missouri Extension website, which can help you with the identification and understanding of this pest. These resources can be found at https://ipm.missouri.edu/IPCM/.
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The phone has been ringing at the Missouri University Extension in Holt County, regarding armyworm damage, according to Regional Agronomist Wayne Flanary. Mr. Flanary said one of those calls was from Daviess County. Calls have been received from most all counties in northwest Missouri, including Harrison, Caldwell, DeKalb and Ray.
Mr. Flanary said growers should actively scout grass pastures for this pest. Scouting is best conducted late in evening or early morning because the worms typically feed at night. Worms will attack grass pastures, winter wheat and corn.
Armyworm attack and defoliate grass plants. There are two to three generations per year with most damage occurring from this pest in May and June.
Larvae feed for three to four weeks; however, 80% of the damage occurs during the last five days of larval feeding. When all food is consumed, the larvae will move to a different site giving the appearance of moving in hordes.
During the day, larvae will be curled up under the ground litter in pastures.
Check with your local dealer regarding pesticides.
Dense grass canopies may hinder insecticide reaching the larvae. Also, larger worms are harder to control than smaller worms. If possible, spray at dusk or at night which provides better control as worms will be on plants and will be more likely to encounter the insecticide.
For more information, contact Wayne Flanary, Regional Agronomist, at 660-446-3724, University of Missouri Extension.