How do we find and stop fall armyworms and sod webworms in our HOA's common turf?

By OurHOA · General information · Revised October 29, 2026

How an HOA board confirms fall armyworms or sod webworms with a soap flush, sets a treatment trigger and times a spot treatment in TX, FL and CO common turf.

Part of the HOA board handbook: vendors, projects and upkeep.

The short answer

Chewed-down brown patches that seem to appear overnight in late summer or fall are often caterpillars. In Texas and Florida common turf, the usual culprits are the fall armyworm and the tropical sod webworm. In Colorado bluegrass, they are sod webworms. A bucket of soapy water brings all of them to the surface in a few minutes, and that count should decide whether the board pays for a spray. Texas A&M AgriLife says armyworm outbreaks are hard to predict, tend to follow rain or irrigation in late summer and early fall, and are usually small. Parasitic wasps, flies, beetles and birds keep most populations in check. The board's job is fast detection: someone walks the turf after a rainy stretch, flushes any suspicious patch, and the contractor spot treats only when the count is high and the larvae are still small. This is general education. Pesticide labels, state licensing rules and your governing documents control what your association may do.

Figure out which caterpillar you have

Fall armyworm. The Texas A&M fact sheet describes larvae up to about 1.5 inches long, tan to green, with a brown or black head marked by a white inverted Y and four large spots on the last body segment. They feed for 2 to 3 weeks, and a generation takes about 28 days, so a second wave can follow the first within a month. UF/IFAS says they damage turf in spring as well as fall, evenly across a large area. Tropical sod webworm. UF/IFAS says it prefers St. Augustinegrass and is most active from spring through fall, all year in South Florida. Mature larvae are grayish green and 3/4 to 1 inch long. They feed at night, dawn and dusk and rest curled below the blades during the day. Look for window feeding, where the leaf surface is scraped off and leaves a nearly clear patch, ragged blades shorter than the grass around them, and piles of bright green droppings. Colorado sod webworms. Colorado State University names two species in Colorado turf, the cranberry girdler and the vagabond crambus. The larvae live in silk tunnels, feed at night and leave small brown patches of closely clipped grass that spread. Flocks of birds probing the turf are often the first sign. CSU's caution applies everywhere: lawn diseases cause brown patches too. Our guides on chinch bugs and on large patch and take-all root rot cover the usual look-alikes in St. Augustine.

Run a soap flush and count

A volunteer can do this. Either recipe works: - UF/IFAS: 1 tablespoon of liquid dish soap in 1 gallon of water, poured over a 4-by-4-foot area of turf next to the damage. Test several spots. - CSU: 1 to 2 fluid ounces of dish soap in 1 gallon of water, poured evenly over one square yard. Larvae should surface within 10 minutes. Flush where green grass meets brown. The caterpillars have already left the dead spots. For fall armyworms, AgriLife's method is to count the larvae in a square foot at 8 sites, add the counts and divide by 8. Include spots away from the edges of the turf, because numbers are often heaviest along the margins, and sometimes only the margins need treatment. Log the date, location, count and larva size, with a photo next to a coin. If nobody can tell what they are, UF/IFAS suggests sending pictures or a turf sample to the county Extension office.

Decide whether to treat

Adopt the published numbers as the board's trigger and write them into the landscape contract, so a treatment is never sold without a count: - Fall armyworms in lawns: AgriLife says to consider treatment when counts average three or more worms per square foot. - Colorado sod webworms: CSU says to consider treatment at 15 or more larvae per square yard in healthy turf, or 5 or more per square yard in stressed turf. - Tropical sod webworms: UF/IFAS gives no count. It says a lawn with no other stress may recover on its own, a stressed lawn may need help, and any treatment should be a spot treatment of the affected areas. Then look at the size. NC State says insecticides are generally ineffective against large armyworm larvae, which are likely to finish feeding and burrow in to pupate. AgriLife says the last two of the five larval stages eat 85 percent of the foliage the caterpillar will ever eat. A high count of small larvae is the case for treating. A count of full-grown ones usually is not: water the turf and flush again in a few weeks to catch the next generation. CSU says proper irrigation is usually enough for turf to recover from moderate feeding. New sod is the exception: NC State says it is more attractive to fall armyworms and more easily damaged, so check summer sod weekly until the weather cools.

Time the treatment so it works

When the count says treat, give the contractor these conditions in writing: - Treat small larvae. CSU says Bacillus thuringiensis (Bt) and the beneficial nematode Steinernema carpocapsae work only on small, young larvae, and NC State says to treat armyworms while they are relatively small. - Mow and water first. NC State says to mow and lightly irrigate before treating. CSU says to apply 1/2 to 3/4 inch of water beforehand to bring larvae closer to the surface, and to mow first to remove flowering weeds so foraging bees are not sprayed. - Spray late in the day. AgriLife says fall armyworms are most active early in the morning and late in the evening, and CSU advises late afternoon or early evening for sod webworms. - In Colorado, time it to the moths. CSU says to apply two to three weeks after peak moth flight, once the eggs have hatched. - Use a product labeled for the pest and the site. AgriLife lists bifenthrin, carbaryl, permethrin and spinosad among the active ingredients labeled for lawns. Labels change, so the product label sets the rate and any re-entry instructions. - Spot treat the infested area and a margin around it. A whole-property spray kills the natural enemies that keep these caterpillars down between outbreaks. Have the contractor list the active ingredient, area and date on the invoice.

Who may spray association turf

Texas. Occupations Code section 1951.003 says identifying or treating pests of plantings in a park or next to a residence or business, for compensation and including work done as part of someone's employment, is the business of structural pest control. Section 1951.301 requires a business license for that work, and every license holder must employ a certified commercial applicator. Get the company's Texas Department of Agriculture license number before it sprays the common turf. Florida. Section 482.071 makes it unlawful to operate a pest control business without a license from the Department of Agriculture and Consumer Services. The limited landscape certificate in section 482.156 covers weeds in beds and hardscape and pests on ornamental plants, not turf. Ask whether the landscaper's license covers lawn insect work, or hire a licensed lawn and ornamental pest control company. Colorado. The Department of Agriculture says anyone applying pesticides for hire needs a commercial pesticide applicator business license under C.R.S. 35-10-103, including proof of at least $400,000 in liability insurance. Let volunteers scout and a licensed company spray. Our guide on hiring an HOA landscaping contractor covers writing those duties into the scope.

A response timeline, an owner notice and a motion

Sample sequence once someone reports chewed brown patches: - Day 1: a volunteer or the landscaper flushes the edge of each patch and photographs what comes up. - Day 1 or 2: the director who handles grounds compares the count to the contract trigger. Below the trigger, or full-grown larvae: water and watch. - Days 2 to 4: above the trigger with small larvae, the contractor mows, waters and spot treats late in the day. The notice goes up before the work starts. - About a week later: flush the same spots and log the counts. - Three to four weeks out: check again for a second generation, especially after rain. Resod only bare spots that do not fill in. Owner notice: "Caterpillars are feeding on the common grass at [locations]. On [date], a licensed contractor will treat those areas in the late afternoon. Please keep children and pets off the marked areas until the product has dried, as the label directs. Questions go to [contact]." Motion: "Move to authorize [contractor] to spot treat caterpillar damage in the common turf when a soap flush finds [three or more fall armyworms per square foot] [15 or more sod webworms per square yard], at a cost not to exceed $[amount] per treatment, with the active ingredient and treated area reported on each invoice." That lets the contractor act within a day.

Mistakes boards make

- Spraying dead grass. The caterpillars have moved on. Flush the green edge. - Buying a preventive cover spray. AgriLife says preventive treatment normally is not justified for fall armyworms because attacks are sporadic and most eggs die. - Treating full-grown larvae. They are about to pupate, and the spray buys nothing. - Overfeeding the turf. UF/IFAS says fall armyworms are more of a problem on new turf that was heavily fertilized in late summer, and AgriLife says the moths prefer lush growth for laying eggs. Look hard at late-summer nitrogen in the fertilizer schedule. - Waiting for a meeting. Larvae finish feeding in two to three weeks. Pass the standing motion before the season starts.

Sources

These guides are general education for HOA boards and residents, not legal, tax, or financial advice. Rules vary by state and by your community's governing documents - check with a professional for your situation.

More on living with an hoa

Or browse all living with an hoa guides.