Armyworms were spotted in St. Johnsbury and Pawlet this week. Please don’t panic but do scout your corn and grass fields for armyworm caterpillars.
True Armyworm, Pseudaletia unipuncta, are typically spotted each year on some acreage in Vermont — crops most affected are grasses including field corn, grass hay and pasture crops. It is important for farmers and consultants to monitor fields. At high populations, armyworms can create significant damage very quickly.
Scout for caterpillars. When mature, they can be almost 1.5 inches long. The caterpillars are usually greenish or brownish, but can be almost black. The sides and back of the caterpillar have light colored stripes running along the body. They normally feed at night and can cause much damage before they mature.
Their preferred foods are grasses including corn, grains, and timothy but they will feed on other plants if grasses are unavailable. Feeding will start on the lower leaves and move upwards. A large population of armyworm caterpillars can strip an entire field in just a few days. When the field is eaten they “march” to adjacent fields. Please note: Corn fields that are reduced or no-tilled or fields infested with grass weeds are most susceptible.
For more information on armyworm, see “When Armyworms Come to Town” and/or True Armyworm resources on the Vermont Crops & Soils webpages. For additional scouting and control options, please contact the following agronomists.
Northwest VT: Heather Darby at (802) 524-6501 or heather.darby@uvm.edu.
Champlain Valley: Jeff Carter at (802) 388-4969 or jeff.carter@uvm.edu.
All other locations: Sid Bosworth at (802) 656-0478 or sid.bosworth@uvm.edu.