Armyworms Guide

Armyworms are the caterpillar (larval) form of several moth species. As caterpillars, they can cause significant damage to lawns, gardens, crops, and forage grasses. These pests can be highly destructive during their larval stage.

Color

Armyworm caterpillars are typically dark brown, black, or green with distinctive stripes of white, orange, brown, or sometimes yellow running the length of their bodies. A unique upside-down "Y" marking on their head segments makes them easy to identify.

Common Types of Armyworms

There are several species of armyworms, each with slight visual differences but often displaying similar stripes. Each type may prefer different plants for feeding:

• Fall Armyworms: Known to be the most damaging to home lawns and golf courses, their damage is typically noticeable in late summer or early fall.
• Yellowstriped Armyworms: These caterpillars are more general feeders, attacking a wide range of crops, including fruits and flowers.
• Beet Armyworms: Green in color, these caterpillars prefer fruit crops and are less common in the U.S. than fall armyworms.
• True Armyworms: Primarily attracted to weedy grasses, these pests can also damage fruit and vegetable crops.

Size

Armyworm larvae (caterpillars) grow up to 1.5-2 inches long at their largest stage. They hatch from small clusters of 50-150 eggs, which are typically green or white and hidden on the underside of leaves, though they may also be found on surfaces near grassy areas.

Armyworm moths typically have a wingspan of about 1.5 inches across.

Shape

Armyworms hatch from circular eggs laid in clusters near grassy areas. After hatching, they crawl or use silken threads to move, sometimes even catching a ride on the wind.

The larvae go through 5-6 growth stages, known as instars, before reaching their full size in about 10 days in warm weather.

At the end of their larval phase, armyworms form a protective pupa (cocoon) underground, which is about 1.25 inches long and reddish-brown to black in color.

After 1-2 weeks, the adult moth emerges. These moths typically have long antennae and two sets of wings that often display different colors and patterns.

Range

Armyworms are found across much of the United States, with a preference for the warmer climate of the Southern states. True Armyworms are more common east of the Rocky Mountains, and damage from these pests is often first reported in the southeastern U.S.