These spots enlarge, connect, and may include large areas of the lawn under heavy infestation. Severely damaged lawns may be completely lost to sod webworm, especially during the dry season when they suffer from a lack of water. Webworms must be controlled with insecticides if already present in large quantities. To prevent future infestation, lawns should be properly maintained. Excessive applications of nitrogen fertilizers substantially increase the chance of attack by lawn caterpillars.
High nitrogen results in lush growth that attracts egg-laying female moths.
Excessive fertilization and watering can also cause lawn grasses to develop a thick, spongy mat of stems and roots which accumulate in a layer above the soil surface. This spongy mat is an excellent habitat for lawn caterpillars. In general, to avoid substantial damage by sod webworms, look for signs of insect presence especially along margins of the lawn or close to shrubs. Examine the grass in any suspicious, off-color areas to determine if the blades have been chewed. If they look odd, closely examine the soil surface.