Wheat head armyworm is not typically a pest that causes economic harm, although sporadic incidents of major economic damage have been reported. However, this pest is generally not an economic concern for most growers. Characteristic damage is indicated by a small hole bored in the base of florets. Feeding on wheat heads at night is most common. Research in Washington by Diana Roberts and colleagues noted up to 35% yield losses due to this insect in spring wheat trials near Davenport. Larvae developing from these eggs then feed on wheat from May into the summer.
Moths emerge in the spring months and lay eggs on wheat or barley. Armyworms are moth caterpillars that vary in color (gray or green) with a distinct yellow, white, and brown stripe along the body. The inverted Y is the key distinction between fall armyworms and true armyworms, a different species of armyworm that typically infests wheat and oats in spring before moving to corn later in the season.Armyworms can be problematic pests in cereal grains. The determining characteristic of fall armyworms is a distinctive inverted “Y” on the head and face, along with four raised bumps in the shape of a square near the end of the abdomen. Young larvae are greenish with a dark head, while older larvae are mottled with red and brown. Emerging larvae go through six instars (stages of development) before pupation. The rough-looking eggs are covered with gray scales and usually hatch within 4 days of deposit. Eggs are typically laid in masses of 100-200 on light-colored surfaces, such as utility poles, tree limbs and fence posts.
Iowa State University entomologists say the pest can arrive in the Midwest in multiple migrations, with moths being driven on strong south winds of late spring and summer.Ī generation takes about 30 days to complete its summer life cycle. Mid-to-late season summer row-crop scouting in no-till and conventional fields usually finds infestations of several species of armyworms, but in some conditions, fall armyworms can become a serious problem, particularly on extremely late-planted corn.Ī native to tropical regions, fall armyworms can only overwinter in south Texas and Florida, but the adults are strong fliers and are capable of long-distance travel into the northern states.
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