Armyworms

What it looks like

Armyworms are the caterpillars of night-flying moths. The fall armyworm, the most common one in lawns, is brownish green with pale stripes along its sides and a pale upside-down "Y" on its dark head.

The moths fly north from the South each spring and summer, so armyworms often appear suddenly, with several generations a year. Damage usually shows in late summer and fall.

Damage

Armyworms feed in groups and move across a lawn together, eating the grass down to the ground. They leave a sharp line between eaten, brown turf and healthy green grass. New sod is especially at risk. They feed mostly in the early morning and evening.

How nematodes help

The beneficial nematodes in Ecomask wait near the soil surface and attack caterpillars that move through the grass and thatch. In lawn tests, S. carpocapsae (the nematode in Ecomask) was the most effective nematode against armyworms. Because armyworms feed on the grass blades rather than in the soil, results can vary, so treat early, while the caterpillars are small.

How to apply

Treat with Ecomask from May to September, as soon as you see damage. Scanmask also works. Apply in the evening, when the caterpillars come up to feed.

Treat the damaged area and the healthy grass just ahead of it, where the caterpillars are moving.

See How to apply for step-by-step directions, or use the calculator on the Ecomask Spray page to see how much you need.