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Armyworms in No-Till Corn, Wheat, and Pasture

May 11, 2001
In last week's Bulletin (issue no. 6, May 4, 2001), Mike Gray wrote an in-depth article about armyworms in wheat and corn. Since then, reports about armyworms causing damage in no-till corn and wheat have been numerous. Joe Reed, technical service representative with FMC Corp., reported on May 8 that he had found armyworms primarily in fields of no-till corn in Randolph, St. Clair, Madison, and Bond counties. Armyworms also were present in wheat fields, although slightly less prevalent. According to several observers, sizes of armyworm larvae found have ranged from 1/2 inch to 1-1/4 inches long.

Ron Hines, senior research specialist, Dixon Springs Agricultural Center, also witnessed significant defoliation caused by armyworms in grass pastures and grass hay fields in his area. In one 30-acre pasture, nothing but stems is left, a characteristic of armyworm damage in any type of grass crop. The densities at the edges of the pasture were 6 to 12 armyworms per square foot.

In last week's article, Mike provided information about scouting, thresholds, and suggested insecticides for armyworms in wheat and corn. In grass pasture, only malathion and Sevin XLR Plus are suggested for control of armyworms. However, Ron Hines reported poor control (less than 20% control of armyworms less than 1 inch long) with malathion applied at the recommended rate on the 30-acre pasture.

Growers with grass pasture and grass hay fields need to look for armyworms right now before the damage gets out of hand. Lack of scouting may result in a significant lack of grass for livestock. Armyworms often cause significant damage seemingly overnight, so scouting is the only way to detect an infestation before it's too late.--Kevin Steffey

Author: Kevin Steffey


The Pest Management and Crop Development Bulletin
Executive Editor: Kevin Steffey, Extension Entomologist

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