Controlling Armyworms on Lawns

Armyworms are moth larvae (caterpillars) that are pests of lawns and turf areas in the Midwest and southern states. They are called army worms because they 'march' in quantity over an area, feeding on lawns in large masses and moving to the next grassy area as one to continue feeding. Recently there have been hundreds of reports of this insect infesting lawns from all over Monmouth County, as well as other areas of New Jersey. Infestations by the thousands are occurring on lawns, where they feed on leaf blades.

The caterpillars are described as being brown to black in color, with a light stripe running down each side, from 0.25-2.5 inches long. During the day they may 'march' onto driveways, decks, and houses.  At night they feed on lawns and can invade swimming pools as well. There have been reports of quantities of over 100 caterpillars per square foot.

Armyworms are rarely seen infesting turf in our area; they are mainly a pest in the Midwest and southern states. Entomologists at Rutgers theorize that Tropical Storm Allison blew in the adult moths from the Midwestern and southern states several weeks ago. The female moths lay as many as 2000 eggs in lawns at a time. After 6-10 days of incubation, the eggs hatch into small caterpillars that feed on leaf blades. The larval stage lasts 3-4 weeks, when the larvae pupate in cocoons in the soil.

While it is believed that this species of armyworm cannot survive winters in New Jersey, it is not known if there will be more generations this summer, and if those future generations will result in a heavier or lighter infestation than what we are seeing now.

Homeowners can spray their lawns with any pesticide that lists armyworm control on the label. These include products containing the active ingredients diazinon, carbaryl, acephate, or chlorpyrifos. It is recommended that the liquid form of the insecticide be sprayed in the late afternoon or evening. The lawn should not be watered or mowed for 1-3 days after the pesticide treatment. Remember, please read and follow all the label directions including those for protecting yourself and the environment before applying any material.

Additional Information

For more information, contact your Cooperative Extension county office.

See also the following articles in the Landscape, Nursery, and Turf Edition of our Plant and Pest Advisory newsletter:

• "Armyworm Outbreaks in New Jersey Turfgrass" in the June 28, 2001 issue
• "Armyworms: The Next Generation" in the July 26, 2001 issue
• "Initiating Armyworm IPM for Turfgrass" in the August 9, 2001 issue