Fall Armyworms Are On the March (8-22-11)

This week’s turf tip is a repeat serving as an annual reminder that late summer through early fall is the peak season for fall armyworm invasions of well managed turf; especially bermudagrass lawns, athletic fields and golf courses that have been fertilized and watered.

The moths migrate in large numbers and lay as many as a thousand eggs each. During these hot days of summer the eggs hatch in only a few days with the tiny caterpillars feeding almost continuously. When small they may go unnoticed while consuming only a small amount of leaf tissue daily, but nearing their last few days as larvae, they can literally devour an entire lawn almost overnight. Therefore, it is important that a careful scouting regime be established to detect their presence and control them while they are small.

At least once a week during the remaining growing season, randomly check several locations in the lawn by brushing the grass back and forth with your hand, part the blades down to the soil line, and look for coiled light tan or green to nearly black caterpillars. If you care to pick one of them up and look at it straight on, you may notice a small inverted “Y” marking on its forehead. A tip that golf course superintendents use to alert them of their arrival is checking the flags on the greens each morning for small light brown egg masses that have been laid on them by the moths during the night. You might try placing a small flag or white flat stake in your lawn as well. Other indicators of their presence are flocks of birds on your lawn or an abundance of paper wasps hovering close to the turf canopy as both feed on the caterpillars.

Control is not too difficult if the lawn is treated with an appropriate insecticide when the caterpillars are small. Liquid sprays or granules containing active ingredients of bifenthrin, carbaryl, cyfluthrin, lambda-cyhalothrin, permethrin or trichorfon are recommended. For more details refer to Extension publication 2331 Control of Insect Pests in and around the Home Lawn. This publication can be obtained from your local Extension office or downloaded from this website.

Published August 22, 2011

Dr. Wayne Wells is an Extension Professor and Turfgrass Specialist. His mailing address is Department of Plant and Soil Sciences, Mail Stop 9555, Mississippi State, MS 39762. wwells@ext.msstate.edu