Oklahoma residents, particularly those with turfgrasses or certain crops, should be aware of armyworms, a common pest that can cause significant damage to various host plants. According to Oklahoma State University (OSU) Extension, Fall Armyworms (FAW), Spodoptera frugiperda, are making their annual appearance across Oklahoma in various field crops, pasture, and turf. Recent reports show sightings of armyworms in Atoka County.
These surface dwellers occur in large numbers in late summer and fall, often 'marching' from one food source to another, which gives them their common name. Their ability to feed on over 350 plant species, reproduce prolifically, and migrate long distances as adult moths makes FAW a serious economic pest. Unfortunately, relief from this pest typically does not occur until the first 'killing freeze'.
Description and Identification The adult armyworm moth is typically pale brown to grayish brown, with a wingspread of about 1.5 inches and a distinctive small, white spot near the center of each front wing. Eggs are spherical and greenish-white, laid in masses on host plants. Mature larvae are about 1.5 inches long, with a yellowish or grayish ground color, more or less tinged with pink. They have a greenish-brown to black dorsum with a narrow, broken, light median stripe, and a dark stripe on each side that includes black spiracles. A pale orange, mottled, and white-edged subspiracular stripe is also present. FAW eggs are very small and can be difficult to spot on vegetation; it is often the damaging larval stage that will be noticed first. Larvae are generally light tan to light green caterpillars that have a brownish-black head, which may appear orangish. To separate them from other caterpillar pests, look for four large spots at the end of the abdomen and an upside-down 'Y' on their head. As the larva feeds and grows, it will progress through six instars that can last approximately two weeks in warm temperatures and up to a month in cooler temperatures. When done feeding, the larva will burrow into soil to pupate for just over a week and emerge as an adult moth. Armyworms overwinter as pupae or mature larvae that pupate in the spring. Moths emerge, mate, and lay eggs, with larvae feeding for about four weeks, though most damage occurs in the last 10 days of this period. There are four generations per year in Oklahoma.
