Oklahoma State University Stillwater, OK
Oklahoma Alfalfa Oklahoma Cooperative Extension Service Oklahoma Agricultural Experiment Station

DAMAGE BY ARMY CUTWORM
The army cutworm completes one generation per year, which begins when moths return to the plains of western Oklahoma and Kansas from the eastern slopes of the Rocky Mountains where they spend the summer in a resting state called aestivation. The moths lay eggs in October at the soil surface in fields that have little vegetative ground cover, such as new stands of alfalfa and those that have been grazed or harvested in fall. The eggs hatch in fall and the cutworm larvae feed through the fall and winter whenever the temperature exceeds about 50 degrees F. However, most feeding damage occurs from late February to early April as the cutworms reach the largest stages of development.    Although damage to leaves and, at times, complete destruction of foliar growth may be evident, cutworms may not be recognized as the problem because the larvae feed primarily at night and hide by tunneling into soil during daylight hours. Sampling should be conducted by sifting the soil to a depth of 1-2" beneath plants. Insecticide application is warranted if populations reach 2-3 larvae per sq.ft. Damage by the army cutworm occurs only during growth of the first crop of alfalfa, because larvae enter the pupal stage in the soil during April. When adult moths emerge in late April and May, they fly to summer resting areas near the Rocky Mountains. Additional information on control of cutworms can be found in OSU Extension Facts #7150.  Image of army cutworm damage
Richard Berberet, Alfalfa Entomologist  Department of Entomology and Plant Pathology  Oklahoma State University

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