Sod Webworm

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Scientific name: Sub-family Crambinae
Problems they can cause: Large populations will cause large patches of dead or dying turfgrass if not controlled.

What are Sod Webworms?

Sod Webworms are a group of approximately 100 surface and thatch feeding moths and their larvae that can be found in the United States, of which six are important pests of turfgrass.

Signs of Sod Webworm in your lawn

The most obvious sign of infestation can be seen at the time of mowing when small grey-white moths are disturbed by the passing mower. Their short flight is distinctive in its jagged, zigzag pattern. During hot, dry summers, thousands of moths can be seen in the wake of mowers or other equipment traversing a lawn. The larvae of Sod Webworm are small and caterpillar-like. Their coloring is reflective of their diet and can be anywhere along the green to brown spectrum, but all have the distinctive circular spots over the body. The larval stage causes damage by feeding upon the foliage. When populations are high, larval tunnels may be seen through the thinning foliage about the same diameter as a pencil. Sod Webworm larvae are nocturnal feeders.

How to prevent & control Sod Webworms

While Sod Webworms can cause considerable damage and loss to turfgrass, it is important not to overreact to their presence in lawns. Large numbers of adult moths (adults do not feed on turfgrass) does not automatically require treatment, as they do not necessarily result in a large number of larvae. It’s only when large numbers of larvae are observed creating significant damage to a lawn that a control product should be considered.

How to repair lawn damage from Sod Webworms?

The repair of Sod Webworm damage is one of a number of very good reasons to perform core aerations and overseeding of your lawn annually in the fall. Lawns that have experienced turf loss from Sod Webworm should be replanted with species that are endophyte enhanced. Endophytes are fungi that live between the cells of grass plants that are toxic to certain insects that feed on them. Most Sod Webworm damage can be overcome through fertilization and irrigation to encourage the lawn to fill in since Sod Webworm only feeds upon foliage, and in the same vein, damage can be mitigated by sticking to proper lawn maintenance practices.

Helpful tips

Sod Webworms are nocturnal feeders so obtaining a conclusive diagnosis requires flushing them from the soil with an irritating drench of approximately two tablespoons of lemon-scented dish soap in two gallons. Apply this drench with a garden watering can to an area about two-feet square. After a few minutes, any caterpillars present in the thatch will come to the surface to escape the soap.