As the spring season warms up, lawns come alive with all kinds of pests, including the sod webworm, a caterpillar that usually invades and damages lawns from May to July and then reappears in the fall. According to Sod Solutions, this is the time to be on the lookout for this destructive lawn pest, which lives primarily in the southeastern region of the U.S. and can be active year-round in southernmost regions, where they peak from September through November.
The University of Florida IFAS Extension notes that tropical sod webworms prefer newly established warm-season turfgrass found in lawns, parks, commercial landscapes, sports fields, and golf courses. They start off as creamy-white eggs that are laid in clusters on blades of grass and thatch areas of your lawn by small dingy-brown adult moths. Those eggs rapidly grow into caterpillars about an inch long, with four parallel rows of dark spots on their abdomen, that burrow and emerge to feed at night. It’s all that midnight snacking that does the most damage to turfgrass.
How to Identify a Sod Webworm Invasion
So how can you tell if your lawn has been invaded by sod webworms?
- Look for transparent blades of grass. The juvenile caterpillars eat the green from the blades, leaving only the veining structure so that it appears transparent.
- Find notched blades of grass. Mature caterpillars feed on the blades, leaving notches on the sides.
- Watch out for frass. The caterpillars can sometimes be seen curled up and surrounded by frass, the fresh green fecal pellets found in the thatch.
- Do a soap flush. For a small area, mix 2 ounces of liquid dish detergent to 1 gallon of water and pour it within a 12-inch circle. For larger areas, mix at least 1 gallon of a solution with 2 parts water to 1 part liquid dish detergent. Pour the mixture and wait a few minutes. The liquid will force the sod webworms – and other insects – to the surface, where you can see them on the blades of grass and identify them.
- Look for brown or straw-yellow colored turfgrass. This, plus the emergence of more weeds as the turfgrass weakens, is another sign of damage.
How to Prevent and Treat Sod Webworm Infestation
Are there ways to prevent and treat sod webworm infestation? Here are some chemical and non-chemical options to keep your turfgrass healthy, less prone to pests, and faster to recover from pest damage.
Non-Chemical Lawn Treatments
- Mow your lawn the right way. Find out the proper mowing height that’s recommended for the variety of turfgrass you have in your yard and never cut more than 1/3 of the blade height in one mowing.
- Reduce thatch. Mowing at the correct height and frequency will reduce thatch buildup.
- Don’t overwater. Your grass only needs about 1 inch of water per week.
- Turn off flood lights. Moths are attracted to the lights at night.
- Don’t over-fertilize. Overfertilizing is a leading cause of caterpillar infestations.
Chemical Lawn Treatments
Chemicals are used to suppress caterpillar larvae when they’re feeding. Before using an insecticide, sample the thatch for sod webworms to see how many are present. For best results:
- Apply insecticides in the late afternoon or early evening.
- Look for products that contain the active ingredients Chlorantraniliprole, Bifenthrin, Lambda-Cyhalothrin, and Trichlorfon.
- Follow all label directions to use the proper amount of chemical, apply the chemical correctly, and help you with properly adding any other compounds for better effectiveness.
- Fertilize properly. Fertilizer won’t treat pest infestations but will keep your lawn strong and healthy to resist damage.
Keeping your lawn healthy, knowing how to recognize the signs of any lawn pest infestations, and learning the best way to apply treatments will help keep your lawn green and lush when it’s time to enjoy your outdoor living.