In Colorado, armyworm is mostly a pest of corn and spring grains, with only occasional infestations occuring in winter wheat. Distribution Armyworm is found east of the Rockies in the United States and Canada and occurs in eastern Colorado and in the San Luis Valley. Best Management Practices Armyworm outbreaks occur only occasionally because they have many natural enemies that usually prevent the development of economically significant infestations. Because of the sporadic and unpredictable nature of armyworm outbreaks, management options are limited to insecticides. Scout for armyworm in field margins, low areas with rank growth, or areas of lodged plants.
Action thresholds for the true armyworm in field corn and small grains.
2 larvae per square foot insecticides labeled for the control of this pest can be found in the most recent version of the High Plains Integrated Pest Management Guide for Colorado, Montana, Western Nebraska and Wyoming , which is available from Cooperative Extension in any of these states. 1 Colorado State University Cooperative Extension entomologist and professor, bioagricultural sciences and pest management. Go to top of this page. Updated Wednesday, May 02, 2001. Contact Cooperative Extension Web Manager .