Short Answer: Sod webworm damage shows up on Palm Beach St. Augustine and Bermuda lawns starting in June as small, irregular patches of close-cropped, ragged-looking turf that spread outward over a few weeks. Look for tiny green pellet droppings in the thatch, white or tan moths flying low at dusk, and notched grass blades. Confirm with a soap flush, then treat with a labeled insecticide like bifenthrin or chlorantraniliprole, watered in lightly. Most lawns recover within three to five weeks with proper irrigation and fertility. Below is the diagnostic walkthrough and the treatment options we use across Boca Raton, Delray Beach, West Palm Beach, and the rest of our service area.
If you have stepped onto your Boca Raton or Delray Beach lawn at dusk lately and watched a small cloud of pale moths lift off as you walked, you are looking at the front edge of sod webworm season. Those moths are not the problem. Their offspring, the caterpillars feeding under your St. Augustine canopy right now, are the problem. And June is exactly when Palm Beach County homeowners start calling us with a familiar story. The grass looks fine one week. The next week there are quarter-sized patches that look mowed shorter than the rest of the lawn. Two weeks after that, those quarter-sized patches have merged into ragged brown areas the size of a beach towel.
We see this every June, and it is not a sign that you did something wrong. Sod webworms are part of the coastal Florida landscape. The warm winters and steady humidity we get from West Palm Beach down through Pompano Beach mean populations build through spring and explode in June. Here is how to know whether you have them, what your options are, and what a realistic recovery looks like.
What Sod Webworms Actually Are
The damage you are seeing is from the larvae of small lawn moths in the genus Crambidae. The adult moths are the half-inch tan or pale gray fliers you see darting just above the turf at sunset. They lay eggs on grass blades, and the eggs hatch into tiny caterpillars that feed at night and hide in silk-lined tunnels in the thatch during the day.
The caterpillars themselves are pale green to grayish, with dark spots running down the body, and they curl up tight when disturbed. A mature larva is about three-quarters of an inch long. They chew notches out of grass blades and eventually mow the leaf right down to the crown, which is why the damaged patches look closer-cropped than the rest of the lawn.
In Palm Beach County we typically see two to three overlapping generations between late spring and fall. The June generation is the one that catches homeowners off guard because populations are growing and the damage suddenly becomes visible after weeks of quiet feeding.
How to Tell Sod Webworm Damage From Drought or Disease
The reason this pest is so commonly missed is that the early damage looks like a lot of other things. Here is how we tell them apart in the field across Boynton Beach and Lake Worth lawns.
Drought damage shows up first on slopes, west-facing sides, and areas the irrigation does not reach. The grass blades fold lengthwise, take on a bluish-gray cast, and footprints linger. Sod webworm damage shows up in irregular patches across irrigated areas with no logical connection to sun or slope.
Fungal disease like gray leaf spot or take-all root rot tends to follow distinct ring or spot patterns and often shows discolored or lesioned blades when you look closely. Sod webworm damage shows clean-cut, notched blades with no lesions, and the patches expand outward at the edges rather than developing in rings.
Chinch bug damage, which also peaks in coastal South Florida, tends to start in sun-baked spots along driveways, sidewalks, and curbs. Sod webworm damage is more often in the middle of the lawn where the canopy is densest, because that is where the caterpillars find the most cover.
The Five-Minute Soap Flush Test
If you want to confirm sod webworms in your own yard before calling anyone, here is the test we walk Boca Raton and Coconut Creek customers through over the phone.
Mix two tablespoons of lemon-scented dish soap into two gallons of water in a watering can. Pick a spot at the edge of a suspicious patch, where damaged turf meets healthy turf. Pour the soapy water slowly over a two-foot-by-two-foot area. Wait three to five minutes.
If sod webworms are present, the soap irritates them and they crawl to the surface. You will see pale green caterpillars wriggling in the grass. Two or three is normal background population. More than ten in that small area is an active infestation that warrants treatment. While you are looking, scan the thatch for the small green pellet droppings (called frass) that are a dead giveaway. Frass plus moths plus close-cropped patches is the trifecta.
What to Do This Week If You Have Confirmed Webworms
Once you have confirmed the pest, the goal is to stop active feeding quickly so the existing damage does not expand, then support the lawn through recovery.
Bifenthrin is the most common active ingredient in over-the-counter granular and liquid lawn insect products labeled for sod webworms. It works on contact and gives about two to four weeks of residual control. Chlorantraniliprole (sold under several brand names) is a more targeted, slower-acting option that affects caterpillars specifically and is gentler on beneficial insects. Spinosad is another option for homeowners who want a product derived from a soil bacterium, though it breaks down quickly in sun and needs more careful timing.
Whatever product you use, apply in the late afternoon or early evening, when the caterpillars are about to become active. Water in lightly afterward (about a quarter inch) to move the product into the thatch where the larvae live. Do not irrigate heavily for 24 to 48 hours after treatment.
Skip the product entirely if your population was three or fewer in the soap flush. Healthy St. Augustine and Bermuda can outgrow light webworm pressure without intervention, and unnecessary applications kill beneficial predators that help keep populations in check.
What Recovery Actually Looks Like
This is where we have to set honest expectations. Sod webworms damage the leaves but rarely kill the crowns or stolons of healthy St. Augustine. That means most damaged lawns regrow on their own once the active feeding stops, provided the irrigation and fertility are dialed in.
For a typical Palm Beach County lawn after a confirmed webworm event, here is the timeline we see:
- Week 1 after treatment: feeding stops, no new damage, existing patches still look bad.
- Week 2 to 3: new green growth begins emerging from runners across damaged areas.
- Week 4 to 5: most patches under a foot across have closed in.
- Week 6 to 8: large patches (two to three feet) are filling but may still show some thinness.
If a patch is still bare at the eight-week mark, the crowns themselves likely died (often from combined stress with disease or drought), and that area will need plugs or partial resodding.
Why Coastal Lawns Get Hit Harder
One thing we have noticed across Palm Beach, Delray Beach, and the barrier-island properties: salt-influenced soil, sandy drainage, and consistent humidity create the perfect environment for webworm pressure. Sandy soil dries faster after irrigation, which keeps thatch conditions ideal for the caterpillars. The constant humidity off the Atlantic means the moths stay active longer into the night. Coastal homeowners often need to monitor more aggressively than inland yards.
Salt exposure also stresses St. Augustine slightly, which means a lawn that is already battling salt spray, sandy soil, and summer heat has fewer reserves to outgrow webworm feeding. The customers who get the best results in coastal Palm Beach are the ones who pair pest treatment with consistent fertility, because the lawn needs the nutrients to push new growth.
When to Call a Professional
For light pressure caught early, a homeowner with a soap flush, a labeled product, and a hose can handle it. We are happy to talk you through that on the phone.
Call us instead if any of these apply. You have damage covering more than a quarter of the lawn. The patches are still spreading two weeks after a home application. You are uncertain whether what you are seeing is webworms, chinch bugs, or disease. You have pets or kids on the lawn daily and want a licensed applicator handling product selection and rates. Or you simply do not want to spend Saturdays on diagnosis and treatment.
A professional visit also gives us the chance to check for the other June pests that often run alongside webworms in our area, including chinch bugs in sun-baked edges and tropical sod webworm cousins like the fiery skipper. Often what looks like one problem is actually two overlapping pressures, and treating both at once saves you a second service call.
What to Do Next
If you have walked your lawn and confirmed webworms, or if you are looking at patches and would rather have a trained set of eyes diagnose what is happening, we can help. We treat sod webworms across the Palm Beaches every June, and our techs know what coastal St. Augustine can handle and how fast it should bounce back.
Lawn Squad of The Palm Beaches serves Boca Raton, Boynton Beach, Coconut Creek, Deerfield Beach, Delray Beach, Lake Worth Beach, Lake Worth, Palm Beach, Pompano Beach, and West Palm Beach.
Call us at 561-621-9217 or request a free quote at lawnsquad.com. Our VitaminLawn program is built specifically for coastal Florida St. Augustine, Bermuda, and Zoysia lawns, with sandy-soil nutrition, salt tolerance, and integrated pest monitoring built into every visit. Most homeowners on the program see fewer surprise pest events because we are walking the lawn every six to eight weeks and catching pressure before damage gets visible.
