Common in summer
Armyworms in the Lawn: Signs and How to Stop Them
Fall armyworms are caterpillars that can chew a lawn from green to brown in just a few days in late summer, especially across the South and transition zone. They eat the grass blades — not the roots — and often march across the lawn in an 'army,' so the damage spreads fast. The good news: a healthy lawn, bermuda especially, usually grows back once they're gone.
How to tell
- Large areas thinning or browning very fast — sometimes overnight — often spreading like a moving front.
- Up close, the blades are chewed, ragged, and see-through rather than evenly drought-browned.
- Lots of birds suddenly working the lawn — they're eating the caterpillars.
- Green-to-brown striped caterpillars (up to ~1.5") with a pale inverted 'Y' on the head, most active at dawn and dusk.
What to do
- Step 1
Confirm with a soapy-water flush
Before you do anything, confirm it: mix a couple of tablespoons of dish soap into a gallon of water and pour it over a square yard where green meets brown. Armyworms surface within a few minutes if they're there. Check early morning or evening, when they feed — they hide near the soil in the heat of the day.
- Step 2
Treat a confirmed, active infestation
If you find an active infestation, choose an insecticide labeled for armyworms and apply it in the late afternoon or evening, when the caterpillars are feeding — smaller, younger larvae are far easier to control. Treat the damaged area and a buffer around it.
Always read and follow the product label — it is the legal authority on rates, timing, and safety. These windows are regional estimates, not a prescription; defer to the label and your local extension office.
- Step 3
Water to recover — and feed only when it's growing
Once the worms are gone, keep the lawn watered so it can rebuild. If it's actively growing — not heat- or drought-stressed, and not a cool-season lawn in summer — a light feeding helps it bounce back; otherwise hold the fertilizer and let water do the work. Bermuda and other spreading grasses usually green back up from the crowns within a couple of weeks; bunch-type lawns like tall fescue may need bare spots reseeded in the fall.
Never exceed ~1 lb of nitrogen per 1,000 sq ft in a feeding, and never feed a heat- or drought-stressed lawn. Always read and follow the product label — it is the legal authority on rates, timing, and safety. These windows are regional estimates, not a prescription; defer to the label and your local extension office.
Preventing it next season
There's no reliable preventer the way there is for grubs — armyworms blow in on late-summer moth flights — so the key is scouting. Watch for sudden bird activity or a neighbor's lawn going brown in late summer, and check early: small larvae caught early are far easier to stop than a full-grown army.
Frequently asked questions
- How fast can armyworms destroy a lawn?
- Very fast — a large brood can chew a lawn from green to brown in just a few days, which is why scouting in late summer matters. Catching them while the caterpillars are small makes control much easier.
- Will my lawn recover from armyworms?
- Usually yes. Armyworms eat the leaf blades, not the crowns and roots, so a well-watered lawn — bermuda especially — typically greens back up within a couple of weeks. Bare spots in bunch-type lawns like tall fescue are reseeded in the fall.
- How do I check for armyworms?
- Pour soapy water (a couple of tablespoons of dish soap per gallon) over a square yard at the edge of the damage. If it's armyworms, the caterpillars come to the surface within a few minutes. Check at dawn or dusk, when they're feeding.