Armyworm of lawn

Disease Information


 Mythimna unipuncta

Symptoms and damage

Armyworms attack many different kinds of plants. When food is scarce, they will move to plants that are not normally attacked. Thus, armyworms can be found on nearly any plant as they migrate in search of edible foliage. Besides warm-season turfgrasses, plants attacked by armyworms include grain and forage sorghum, corn, small grains, sweet potato, beans, turnip, clover, tobacco, spinach, cucumber, potatoes, tomatoes, cowpeas, cabbage, bluegrass and others.

Damage consists of foliage consumption. The small larvae will chew the green layer from the leaves and leave a clearing or “window pane” effect. The first three instars do very little feeding while the last two instars consume 85% of the total foliage consumed.

COMMENTS on disease

Weather and multiple natural enemies usually act together to keep populations under control. Parasites such as wasps and flies are very effective against armyworms. Predators, such as ground beetles, are also effective in limiting outbreaks. Birds, skunks and rodents also consume large numbers of larvae and pupae. Diseases such as insect viruses and fungi can also be important.


Armyworms should be controlled when they occur in large numbers or plant damage is becoming excessive. This will be apparent in turfgrass by examining the grass blades. Damaged areas of lawns appear off-color and eventually turn brown as damage progresses from small windowpane strips of damaged leaf tissue to destruction of entire leaves. Armyworms feed any time of the day or night, but are most active early in the morning or late in the evening.

Treat with a labeled insecticide when leaf damage becomes evident and large numbers of caterpillars are visible. Effective, low-impact insecticides include halofenozide (small caterpillars only) and spinosad. Bacillus thuringiensis (Bt) products are widely available and will selectively control small armyworm larvae without harm to beneficial insects; however, Bt residues does not last on turf for more than 1-2 days. Conventional insecticide choices for armyworms in lawns include bifenthrin, carbaryl, esfenvalerate, permethrin and others.


Share this article