How to Control Armyworms in the Lawn

These militant moth larvae can really chow down on your grass if you don’t fight back.

Aggressive little grass-eaters, armyworms will help themselves to your lawn if not stopped in their tracks. Patches of brown turf and chewed-up blades are a call for help—your grass needs saving and it’s time to take action. Here’s the lowdown on these tiny tyrants, plus how to kill armyworms and get your grass growing again if they’ve tried to conquer your lawn.

What Do Armyworms Look Like?

First, let’s be sure you know what you’re dealing with: Armyworms, which are moth larvae, are light green or tan in their earliest stages and become dark green or brown as they grow. Fully formed caterpillars are hairless, 1-½ to 2 inches long, and have green, yellow, or brown stripes running down their body, and a Y-shaped mark on their head.

Where do Armyworms Live?

Because most can’t survive freezing temps, armyworms are largely found in the South where their snack of choice is bermudagrass. That doesn’t mean your cool-season turf is necessarily safe, though. In summer, adult moths will ride the winds of a tropical storm, and each one will lay thousands of eggs up North. The larvae from those moths are commonly called fall armyworms, and they’ll happily chow down on your lawn before a big chill sets in.

What Damage do Armyworms Cause?

Armyworms have a seemingly endless appetite for grass. Moving as a group, they’ll march across a lawn in a matter of days and leave a yard full of brown, chewed-up grass in their wake. They quickly move onto the next feeding opportunity, so if your neighbor mentions an armyworm problem, get prepared.

What Treatment Kills Armyworms?

Armyworms are surface feeders—if your lawn is infested you’ll see them chomping on the tips of grass blades—and they’re easily controlled by insecticides when caught early in their infestation. If you see armyworm damage or find the pests in your grass, apply Scotts® GrubEx®. Follow all of the label directions, and make sure your lawn is dry when you get out there with your spreader. Then, water regularly—the most severe damage occurs when armyworms attack in hot, dry weather.

How Can I Help My Lawn Recover?

After an infestation, your grass blades may be chewed up, but here’s the good news: Armyworm feeding doesn’t hurt the all-important plant crowns. Your lawn should bounce back with the right plan.

Hot, dry weather isn’t great on any lawn, much less one stressed out by armyworms. Keep your lawn adequately watered to encourage regrowth after armyworm damage.
Apply Scotts® Turf Builder® Lawn Food to help strengthen your lawn and promote growth after armyworm stress. It works on all lawn types and can be applied in any season. If you put down fertilizer right before the attack, wait at least a month before applying another round.
Warm-season grass types are hardier and usually recover with fertilizer, but Northern lawns may need extra help. If that’s the case, you can overseed your lawn to thicken it back up. Use a spreader to apply a premium quality grass seed like Scotts® Turf Builder® Thick'R Lawn™ Sun & Shade, following all label directions.

Don’t let militant moth larvae take you by surprise. If you suspect armyworms are plotting an invasion, get out there and protect your turf. A lush lawn is worth the fight.