Crop & Pest Report

Accessibility


| Share

Armyworm in Rye (06/25/20)

Armyworms were reported causing economic defoliation and clipping heads in spring planted rye in Richland County (Source: Chandra Langseth, Richland County Extension office) and required an insecticide treatment.

Armyworms were reported causing economic defoliation and clipping heads in spring planted rye in Richland County (Source: Chandra Langseth, Richland County Extension office) and required an insecticide treatment. Armyworms migrate into North Dakota on southerly winds each year. The moths are attracted to lodged small grain fields for egg laying. Cool, wet weather are favorable conditions for armyworm outbreaks.

Scout for armyworm larvae and feeding injury including leaf defoliation, worm frass (droppings) around the base of plants and any clipped heads. Look for larvae beneath plant debris around the base of plants and on heads of cereal grains. Full-grown larvae are green to black, smooth skinned with longitudinal stripes and mature at a length of 1½ to 2 inches.

An insecticide treatment is recommended at the Economic Threshold for small grains (wheat, barley, oats, rye):

 

  • Preheading: Treat when four or more larvae per square foot are present.
  • Heading (head clipping): Treat when two or more worms per square foot are present.
  • Armyworms are ¾ to 1¼ inches long.
  • Leaf feeding or head clipping is evident.

If armyworms are more than 1½ inches long, control is not likely to provide economic return. In this situation, the damage already is done and larvae are getting ready to pupate (a non-feeding stage where it transforms into the adult moth). The best timing for an insecticide application is in the evenings or on cloudy days when armyworms are feeding actively. Check preharvest intervals (PHI) if the treatment is close to the crop harvest. For more information, please read the NDSU Extension publication

The Armyworm and the Army Cutworm E830.

ent.1

 

 

Janet J. Knodel

Extension Entomologist

This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

USDA logo

Creative Commons License
Feel free to use and share this content, but please do so under the conditions of our Creative Commons license and our Rules for Use. Thanks.