How to Manage Pests

The UC Guide to Healthy Lawns

Cutworms and armyworms — Agrotis spp., Peridroma saucia, and Mythimna (= Pseudaletia) unipuncta

Granulate cutworm adult

Granulate cutwom larva

Variegated cutworm larva

Black cutworm larva

Parasitized armyworms

Click on images to enlarge.

Identification

Adults are dull brown or grayish, relatively large, up to 1-1/2 inches (3.8 cm) long, night-active moths. Larvae are caterpillars that are up to 2 inches (5 cm) long at maturity and often curl up and lie still when disturbed. The large size and behavior of larvae distinguish them from lawn moth caterpillars.

Hosts

All turfgrass species

Damage

Cutworm and armyworm larvae chew and cut leaves around the crown. Damage begins in small, irregular spots and spreads to patches extending many feet in width. Armyworms, especially, prefer moist areas.

Monitoring information

Cutworms and armyworms are active from early spring through the fall. Look for fat, dull gray, green, or brownish larvae up to 2 inches (5 cm) long with a drench test. Inspect outdoor lights around dawn for 1-1/4 inch (3.2 cm) brownish to gray moths.

Management

Reduce thatch and eliminate soggy areas. Larvae have some natural enemies, such as braconid wasps and tachinid flies. If more than 5 larvae per square yard are present, you may need to treat. Beneficial nematodes or an application of Bacillus thuringiensis (Bt) may be effective against young caterpillars. Other safe products are available.

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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