Army Cutworms - April 25, 2024 - Amy Timmerman, Extension Educator
Note: Click on the 
button for Full Screen; then click on the en CC button for Closed Captioning; then click on play and so that you are able to read the captioning.
(Plays best in Chrome)
- [0:00] This is Amy Timmerman with this weeks Extension update.
- [0:04] With the recent nice warm weather in Nebraska,
- [0:06] army cutworms are likely starting to show up.
- [0:09] Thus it is an important time to scout for army cutworm,
- [0:12] particularly in winter wheat and alfalfa.
- [0:15] Of the many cutworm species in Nebraska,
- [0:17] the army cutworm is the most damaging in western Nebraska,
- [0:20] causing injury to alfalfa, wheat, and various rangeland grasses.
- [0:25] There have also been reports of army cutworm feeding on
- [0:28] pulse crop seedlings, such as field peas and chickpeas.
- [0:32] Economic damage from other cutworms, such as the pale western cutworm,
- [0:36] dark-sided cutworm and variegated cutworm, is rare.
- [0:40] Army cutworms may also be found in lawns and turfgrass.
- [0:44] In late September and October, army cutworm moths laid their
- [0:48] eggs directly on bare soil, such as in newly planted
- [0:51] winter wheat or heavily grazed patches of range.
- [0:55] Females can lay 1,000-3,000 eggs.
- [0:59] After rainfall, these eggs hatched over an extended period,
- [1:02] leading to a variety of caterpillar sizes feeding and developing
- [1:05] as long as temperatures were adequate (approximately higher than 45°F).
- [1:11] When the weather turned colder, the caterpillars burrowed down
- [1:15] into the soil to spend their winter.
- [1:17] Because army cutworms overwinter in Nebraska as larvae in the soil,
- [1:21] they are one of the first caterpillars to be seen in the spring.
- [1:24] Now, caterpillars will be emerging from the soil on warmer days to feed.
- [1:29] Scouting fields for army cutworms now and in the coming weeks is recommended.
- [1:33] As we continue into early spring and winter wheat breaks dormancy,
- [1:38] this would be a great time to scout for cutworm activity.
- [1:42] Army cutworm larvae are greenish-brown to greenish-grey
- [1:45] caterpillars, approximately ½ to two inches in length.
- [1:49] Feeding damage from army cutworm larvae can vary from grazing leaf tips and
- [1:53] chewing on the sides of wheat seedlings to complete stand reduction.
- [1:59] In infested fields, you may see higher than usual bird activity,
- [2:02] especially in the early morning; birds will often feed on
- [2:06] army cutworm larvae when they are in high numbers.
- [2:09] To scout for army cutworms, use a treatment threshold of
- [2:12] four or more cutworm larvae per square foot of winter wheat or alfalfa.
- [2:17] However, for stressed, thin stands of wheat or newly established alfalfa
- [2:21] stands, use a threshold of two or more larvae per square foot.
- [2:26] New or stressed alfalfa stands for example, stands that suffered from some winterkill
- [2:32] require a lower threshold because they are more prone to damage from cutworms.
- [2:36] Army cutworms only feed at night and seek out dark, sheltered areas during the day.
- [2:42] Turn over clots of loose soil and residue for accurate cutworm counts.
- [2:47] If army cutworm counts are above the threshold,
- [2:50] consider an insecticide application.
- [2:52] Other factors to consider before making treatment decisions
- [2:55] include the crop yield potential and cost of control, as well as the size of
- [3:00] larvae (large larvae indicate completion of damaging stage).
- [3:05] Current information on insecticides labeled for use on alfalfa and winter
- [3:09] wheat for army cutworm can be found in the most recent edition of the
- [3:13] Guide for Weed, Diseases, and Insect Management in Nebraska - EC130.
- [3:18] Note that some of these insecticides are also labeled for the alfalfa weevil
- [3:21] in alfalfa and for use on range and pasture grass for the black grass bug.
- [3:26] Other insect pests in these crops may also be listed.
- [3:30] Always read, understand and follow all pesticide label
- [3:34] instructions carefully before purchase and use.
- [3:37] If you have anyquestions on identifying army cutworms or
- [3:40] management options contact your local extension office.
- [3:43] This has been Amy Timmerman with Nebraska Extension.