Armyworms

Armyworms are light brown to dark tan, mostly hair- less caterpillars (moth larvae) with yellow or brown stripes that run the length of their 11⁄2 to 2–inch long bodies. They are formidable feeders, especially on lawns and young vegetable seedlings. As their name suggests, they will decimate one area, then move in mass to another area in search of additional food.

LARVAE

PUPA

ADULT

LOCATION & SEASON

Armyworms are found throughout the Southwest, Southeast and Northeast regions of the United States. While the “spring” armyworm is most damaging in spring and early summer, the “fall” armyworm does the most damage in late summer and declares war on Oklahoma until the first frost of winter. The infestation begins in late June as adult moths bring arrive from the south. Upon their landing, adult females lay masses of eggs. They can lay up to 1,000 eggs at a time. Larvae hatch out early July and will feed underground for two to three weeks before digging into the soil to pupate. The new generation of moths will emerge about two weeks later. This reproductive cycle will continue through October allowing several generations of armyworms to populate the region.

DETECTION

To detect armyworms, examine plants at night with a flashlight or douse lawn with soapy water, which will bring pests to the surface. Armyworms mainly migrate to a food source in the cool of night, so they can be hard to detect until they begin to inflict damage by eating leaves.

DAMAGE

Armyworms feed on a wide variety of plants but prefer grasses and most turf grasses are highly sought after. They are capable of completely defoliating a lawn in a matter of days if the infestation is heavy enough. Young lawns are particularly susceptible, but they aren’t the only thing on the menu. Young seedlings are demolished as well and often eaten at the base, causing new plants to fall over, similar to cutworm damage.