Tropical Sod Webworms In Lawns: Controlling Tropical Sod Webworm Invasions

Tropical sod webworms in lawns do extensive damage in warm, tropical, or sub-tropical climates. They usually don’t destroy turf unless infestations are severe, but even minor infestations can cause problems for lawns that are already stressed by hot, dry weather.

Signs of Tropical Sod Webworms in Lawns

The pests, which feed exclusively on grass, are the larvae of small moths that you may notice flying around your lawn when disturbed by walking, watering, or mowing. The moths themselves don’t cause any problems, but they lay their eggs in the surface of the soil. It’s the larvae that eat the blades of grass and create tunnels in the thatch. The larvae overwinter in the thatch, then begin feeding on your lawn when the weather gets warm in spring. The pests multiply quickly, producing three or four generations in a season. The first symptoms of tropical sod webworms in lawns, other than the appearance of the moths, include small patches that turn yellow or broth by midsummer. Sunny, dry areas are most susceptible, and the pests aren’t usually found in shady spots. The damage spreads quickly, especially during hot, dry weather. Soon, the grass thins and becomes uneven and ragged. You may also notice thin webbing when the grass is dewy. Birds feeding on your lawn more than usual are a good sign of pests, and they are a big help when it comes to tropical sod webworm control.

How to Manage Tropical Sod Webworms

Controlling tropical sod webworms in the landscape consists of good maintenance. Care for your lawn properly; well-maintained turf is less susceptible to damage. Water and feed regularly, but don’t overfertilize, as fast growth may contribute to the infestation. Mow regularly, but don’t scalp your lawn. Set your mower to 3 inches (8 cm.) and your lawn will be healthier and better able to withstand problems including pests, drought, heat, and other stresses. Pour a mixture of 1 tablespoon dish soap and 1 gallon of water onto infested patches at a rate of about a gallon per square yard. You’ll see larvae coming to the surface in a few minutes. The soap should kill the pests, but if not, destroy them with a rake. Bacillus thuringiensis (Bt), a natural soil bacterium that works well as a pesticide, usually kills pests and has fewer harmful side effects than chemical products. Repeat every five to seven days. Use chemical pesticides only as a last resort and only when you’re absolutely sure webworms are present, as toxic chemicals often create more problems by killing beneficial insects. Use products labeled for tropical webworms and don’t irrigate for 12 to 24 hours.

Mary H. Dyer

A Credentialed Garden Writer, Mary H. Dyer was with Gardening Know How in the very beginning, publishing articles as early as 2007.