Fall armyworms attracted to irrigated lawns 08-13-07

As the dry conditions continue over much of the state, homeowners are watering their lawns and landscape plantings to keep them alive and healthy. Insects also are aware of where the moisture is and will concentrate in those areas to lay their eggs. Fall armyworm adult moths are presently seeking out irrigated lawns at night and are busy depositing egg masses of about 150 eggs, then flying a few feet to deposit another mass until they lay as many as 1,000 eggs.

With the high temperatures these eggs hatch in only a few days into tiny caterpillars that feed continuously on the turf leaf blades. These tiny larvae feed as a group and often go unnoticed by the homeowner until they increase in size and then, in almost one night, can simply devour a lawn. Bermudagrass lawns are most susceptible, but centipede and St. Augustine lawns have been known to be rare targets, particularly under extreme drought conditions.

Regular lawn inspections and insecticide applications upon armyworm detection will help prevent severe fall armyworm damage. At least once a week during the remainder of the summer randomly select locations in the lawn to brush the grass back and forth with your hand, then part the grass down to the soil line and look for coiled light-tan or green to nearly black caterpillars.

They also may have a distinct inverted y marking on their forehead. Control is not too difficult if the lawn is treated with an approved insecticide such as carbaryl, cyfluthrin, permethrin or lambda-cyhalothrin when the larvae are small. Early detection and control are the keys for preventing any appreciable damage to the lawn.

Published August 13, 2007

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