How to Kill & Prevent Armyworms

These caterpillars can completely defoliate your lawn unless you stop them in their tracks.

Armyworms are the larvae of a moth that primarily eat grass blades, but will also eat some vegetables, like beans, cabbage, corn, onion, pepper, pea, and radish. A large armyworm infestation can defoliate an entire lawn in a few days.

What Armyworms Look Like

Armyworms aren't the only larvae you may find living in your lawn. Here's how to identify them:

  • The caterpillars are light green or tan in their early growth stage and dark green or brown in later stages.
  • Full-grown larvae are 1½ to 2 inches long and almost hairless.
  • They have a series of green, yellow, or brown stripes down the length of their bodies.

How Armyworms Can Damage Your Lawn

Largely found in the South, especially on bermuda grass, armyworms can infest lawns and cause severe damage. Adult armyworm moths sometimes ride storm fronts into the North, though, so it's important to keep an eye out in any region. Look for small patches of brown grass with the edges of the blades chewed. Some blades may be completely eaten.

Armyworm Treatment

If you notice an increase in adult moths or spot a mass of furry-looking eggs, you may want to prepare for an infestation. Here's what to look out for and what to do.

Watch for Moths, Eggs, and Damage

  • Adults are tan or brown moths less than an inch long, with a white spot in the middle of each forewing.
  • Egg-laying females attach large clusters of eggs to tree leaves and even fence posts.
  • As larvae move into a lawn, their damage usually becomes apparent starting close to the edges. As they feed, larvae leave brown patches in the lawn and cause grass blades to look ragged. In the case of large infestations, blades may be sheared to the ground.

Treat Early for Best Control

Unusual shifts in weather or variations in insect migration patterns can increase armyworm development while decreasing the amount of natural armyworm predators. The result? An armyworm infestation. If this happens in your yard, you can control armyworms with an insecticide.

Apply Ortho® Bug B Gon® Insect Killer for Lawns if you find armyworms in your lawn—they're surface feeders so you should be able to spot them in the turf. Under small to moderate infestations, although the grass blades may be chewed, the crowns are not damaged by the feeding and can recover if the damaged area is kept well fed and watered. The most severe damage occurs during hot, dry weather, so don't delay armyworm treatment if you think they're attacking your grass.

Help Your Lawn Recover

How you help your lawn recover from an armyworm infestation depends on how big of an infestation you're dealing with and where you're located.

The key to stopping armyworms is keeping an eye out for their presence. Follow these tips and you'll be ready to fight back if armyworms try to invade your lawn.