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Tropical Sod Webworm (Herpetogramma phaeopteralis)
Identification guide for South Florida homeowners.
What Are Sod Webworms?
Sod webworms are the caterpillars of small lawn moths. The larvae chew on grass blades at night, leaving the lawn ragged and thin. In South Florida, where moths can be active much of the year, generations overlap and damage can show up quickly.
How to Identify Them
During the day, you may notice small brownish moths flying up in short zig-zag flights when you walk across the lawn. Look closely at the grass for notched or chewed blades, small green droppings and, in the morning, silk threads in the thatch. Larvae curl up when disturbed and hide in the thatch during the day.
Simple check: Mix a tablespoon or two of liquid dish soap in a gallon of water and pour it over a few square feet at the edge of a damaged area. Caterpillars will come to the surface within a few minutes.
Similar problems:
- Armyworms: larger caterpillars that feed during the day and can move across a lawn quickly. See armyworms.
- Chinch bugs: yellowing patches but no chewed blades. See chinch bugs.
Life Cycle and Habits
Moths lay eggs on grass blades at night. Larvae feed for a few weeks, then pupate in the thatch or soil. Adults emerge to repeat the cycle. Warm weather speeds development.
Signs of Sod Webworms
- Ragged, chewed grass blades and thinning patches
- Small moths flying up from the lawn during the day
- Green droppings in the thatch
- Birds pecking heavily at the lawn
Is it dangerous?
- Property damage
Chewed, thinned lawns and brown patches.
Prevention Tips
- Avoid overfertilizing, which produces tender growth larvae prefer.
- Mow at the recommended height.
- Check the lawn regularly in summer and fall.
About Lawn and Plant Treatment
Pro-Spray's service covers pests in and around your home, not lawn or plant treatment. For turf or plant damage, contact a licensed lawn and ornamental provider or your UF/IFAS county Extension office, which can help confirm the cause and recommend options for your yard.
Why Damage Shows Up "Suddenly"
Webworm damage often seems to appear overnight, but it usually builds for a couple of weeks. Young larvae eat only small amounts, scraping the surface of the blades. As they grow, they eat much more, and the lawn can go from slightly ragged to visibly thin and brown in just a few days. That's why it's worth checking your lawn regularly during summer and fall, especially if you notice moths fluttering up as you walk across the grass in the evening or early morning.
Webworms in Shady vs. Sunny Areas
Webworms can feed anywhere in the lawn, but damage is often easiest to see in sunny areas where the grass is already under heat stress. In shady areas of St. Augustinegrass, where turf is thinner to begin with, even light feeding can leave bare spots.
Helping the Lawn Recover
Once larvae are under control, give the lawn time and the right care. Water according to local guidelines so roots stay healthy, mow at the recommended height for your grass type, and hold off on heavy fertilizing until new growth starts. Most warm-season lawns fill back in from runners if the roots and crowns weren't damaged. If bare patches remain after several weeks of good weather, plugs or new sod may be needed.
Birds Can Be a Clue
Flocks of birds, especially in the early morning, working over the same part of the lawn are often feeding on webworm larvae.
Frequently Asked Questions
What are the little moths in my lawn?
Will my grass recover?
Why are birds pecking my lawn?
How do I check for webworms?
Reviewed October 2026 by Pro-Spray's family-run team
Pests don't wait.
Protect your home today.
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