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Managing Sod Webworms and Cutworms

Protecting Your Lawn from Turf Damaging Insects

Is your lawn suffering from unsightly dead spots? Damage caused by cutworms and sod webworms can often be mistaken by homeowners as symptoms of dryness. Unfortunately, it will take more than just water to return your lawn to a lush, green state if it is suffering from an infestation.
 

What Are Sod Webworms?

Sod webworm adults are often what people would refer to as “lawn moths”. They are often seen darting across the lawn, especially when disturbed. The moths do not harm the lawn; however, their eggs hatch into larvae that get as long as ¾ of an inch. As larvae, they construct tunnels or burrows throughout the thatch layer, sometimes extending into the soil. The name “webworm” is derived from the insect’s habit of lining its tunnel with a silk-like material they produce.
 

Sod Webworm Lifecycle

The adult moths emerge from the lawn in late spring, flying mainly during the evening hours and laying eggs randomly throughout the lawn. The larvae emerge from the egg and begin feeding immediately. Damage is caused by larvae chewing off grass stems and leaves while feeding during the summer and into early fall. The dead patches of grass pull away easily in clumps, revealing masses of silk with the green excrement pellets left by larvae. As mentioned, the symptoms often appear similar to that of dryness.
 

What Are Cutworms?

Cutworms are large, plump, dull-colored grayish-green and brown larvae which viciously chew on grass plants. They live on the soil’s surface or in the thatch layer. During the day they burrow into vertical holes to hide. When nightfall arrives, they emerge from their burrowed hole and feed at the rim of the hole. Stems, leaves, and roots of the grass plants may be injured, leaving yellowish-brown dead patches with a hollow hole in the middle of the circle. A symptom to watch out for is birds – starlings have a keen ability to locate cutworm larvae. When these birds return frequently to an area on the lawn, cutworm larvae may be present.


Cutworm Lifecycle

The adult cutworm appears in the spring as a grayish/brown moth with a 1 to 1 ½ inch wing span. Adult cutworms do not damage lawns. They lay their eggs in the spring during the night, leaving them on grass blades. Larvae emerge and begin feeding as early as June with damage appearing in June/July. Cutworms actually feed at night on grass blades which they chew off close to the base of the plant. Dead patches of grass begin to appear and may be pulled away easily by hand.
 

Management

The best time to treat cutworm and sod webworm infestations is when they are very young, before severe damage occurs. By early fall they will begin to transform into adults and will be much more difficult to control. There are several applications available to help manage these insects. Contact your local Weed Man if you suspect your lawn is affected!
 
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