Armyworms are destructive pests that consume turf grasses, but they'll feed on vegetables and other plants when food is scarce. They eventually become moths, but it's the worm-like larvae stage that cause the most damage. When large numbers are present in your lawn, armyworms may seem to march side-by-side like an army battalion. Heavy infestations can destroy lawn grasses in just a few days.
Armyworm Identification: Several species of armyworms affect lawns and crops in the United States. In the larval stage, they typically measure 1 1/2 to 2 inches long. Their heads may vary in color, but they have a distinctive inverted "Y" mark. Armyworm bodies have a series of green, yellow, red or brown stripes down their sides and backs. Adult armyworm moths measure about 1 1/2 inches across. Their front wings are dark gray with light and dark splotches, but their hind wings are pale gray-white.
Signs/Damage of Armyworms: Small brown lawn patches are often the first clue of an armyworm problem. The pests may leave grass blades ragged or chew just the green layer, creating a transparent “windowpane" look. Grass may be sheared to the ground, creating bare spots in your lawn. When feeding on corn and other plants with larger leaves, these pests may leave rows of matching holes.
How to Control Armyworms: Armyworms feed around the clock, but their most active times are early morning and late evening. Time your treatment to coincide with activity for maximum results. GardenTech® brand offers several highly effective controls to kill armyworms by contact and protect for up to three months:
- Sevin® Insect Killer Granules treat your entire lawn to reach armyworm stages above and below ground. Use a regular lawn spreader for uniform coverage. Then, water the granules immediately to release active ingredients into the soil.
- Sevin® Insect Killer Ready to Spray attaches to a regular garden hose. Spray lawn and garden areas thoroughly, including all surfaces of affected garden plants.
- Sevin® Insect Killer Ready to Use simplifies target spot treatments. Just adjust the spray nozzle and it's ready to kill existing armyworms and protect against future invasions.
Tip: Armyworms often attract starlings, skunks and rodents that feed on larvae hidden in your turf. Large numbers of probing birds or areas of scratched, disturbed lawn may indicate plentiful armyworms.
Always read product labels and follow the instructions carefully, including guidelines for pre-harvest intervals on edible crops.
GardenTech is a registered trademark of Gulfstream Home and Garden, Inc.
Sevin is a registered trademark of Tessenderlo Kerley, Inc.
"Crop Pests photo" by K-State Research and Extension licensed under CC BY 2.0