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How to Manage Pests

The UC Guide to Healthy Lawns

Lawn moths and sod webworms — Nomophila noctuella, Tehama bonifatella, Crambus sperryellus

Adult lawn moth

Lawn moth larvae

Click on images to enlarge.

Identification

Adult moths are 3/4 inch (1.9 cm) long and have an appendage in front of the head resembling a snout. The moth holds its wings close to and over its body at rest, giving it a slender appearance. When disturbed, lawn moths make a short flight close to the grass. Sod webworms are the larvae of lawn moths. The larvae are cream colored, 3/4 inch (1.9 cm) long, and have a distinctive double row of brown or black spots down their backs, located at the base of brown bristles. The spots, bristles, and smaller, more slender size distinguish them from cutworms and armyworms.

Hosts

All turfgrass species, especially annual bluegrass (a common weed in turf), creeping bentgrass, and Kentucky bluegrass

Damage

Damage appears as irregular patches of brown or bare areas. Leaves are chewed or missing. There is no feeding damage to roots. Damage is more severe on drought-stressed turf.

Monitoring information

Look for larvae from early summer to mid-fall. Perform a drench test to find slender, cream-colored larvae. Look for whitish or brownish moths flying close to the grass when disturbed.

Management

Reduce thatch and follow recommended irrigation and fertilization practices. If more than 15 larvae per square yard are found, you may need to treat the area. An application of Bacillus thuringiensis or other safe product may reduce populations. Beneficial nematodes may also be effective if applied when larvae are very young.

Life cycle

For more information on lawn insects, refer to:
Pest Notes: Lawn Insects


Statewide IPM Program, Agriculture and Natural Resources, University of California
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