Army Worms

Army Worm Facts

• Size: Full-grown caterpillars measure about 1 1/2 inches.
• Color: Green, brown or nearly black, with light stripes along the body

Army Worm Behavior

Armyworms got their name from the way large numbers move across a lawn together, eating as they go. Young caterpillars scrape the surface of the blade and leave thin, see-through patches, sometimes called windowpaning. Older ones chew blades down to ragged stubs. In Florida, the heaviest lawn damage tends to come from late summer into fall.

Identifying Armyworms in Florida Lawns

The armyworm Florida homeowners most often find in lawns is the fall armyworm, the caterpillar stage of a night-flying moth. Grown caterpillars reach roughly 1 1/2 inches long. Their color ranges from green to brown to nearly black, with pale stripes running the length of the body.

Telling it apart from other lawn caterpillars:

• A pale, upside-down “Y” on the front of the head
• Four dark spots forming a small square on the back near the rear end
• Tropical sod webworms, another Florida lawn pest, are smaller, under an inch, and leave silk-lined tunnels in the thatch
• Cutworms are plump and smooth and curl into a tight “C” when disturbed

The adult is a gray-brown moth with mottled front wings, about 1 1/2 inches across, that flies at night and comes to lights. Females lay eggs in clusters of 100 or more, covered with fuzzy scales from their bodies.

Habits and diet: caterpillars hide in the thatch during the day and feed mainly at night and in the early morning. They eat many grasses, including St. Augustine and bermudagrass, and in farm fields they are a serious pest of corn and other crops. In warm weather they feed for about two weeks, then pupate in the soil.

In Florida: fall armyworms are common here. They cannot survive cold winters, so they overwinter in South Florida and other warm areas, and the moths spread northward each year. Lawn damage usually peaks from late summer into fall. See signs of an armyworm infestation.