Fall armyworms may be the main cause of a dry and brittle lawn due to how quickly they can march across your yard and eat away at your beautiful green grass. As a result, your lawn may look as though a winter freeze has already made its way through.
To help keep armyworms from damaging your lawn, Manuel Chavarria, Ph.D., Texas A&M AgriLife Extension Service turfgrass physiology specialist and assistant professor at the Texas A&M College of Agriculture and Life Sciences Department of Soil and Crop Sciences, has shared some tips and hints to address the problem.
Tip 1: Identifying armyworms
Chavarria said armyworms are most easily detected by visual inspection. Larvae can be identified by their distinct green, brown to gray coloration with a whitish, inverted “Y” shape between their eyes. Mature larvae can be an inch long.
“Armyworms are often most visible during early morning and late evening hours,” Chavarria said.
Early signs of damage appear as transparent tips of grass blades. As the infestation progresses, large spots of leafless grass start to appear.
Armyworms are picky eaters and prefer well managed and fertilized grass. The damage can rapidly progress if left untreaded.
Tip 2: How to treat infestations
Chavarria recommends treating armyworms based on the infestation severity. The infestation can range from low to medium to extreme, depending on their numbers per square foot of lawn.
Low infestation would be one to two armyworms per square foot and may cause minimal damage. This would not require immediate intervention if the lawn is healthy.
Three to five armyworms per square foot is a medium infestation and can create visible thinning of the lawn. The damage can quickly escalate so treatment should be considered at this stage.
An extreme infestation with six or more armyworms per square foot can inflict damage to a lawn in two to three days. Treatment should be immediate to prevent permanent damage to the yard.
David Kerns, Ph.D., AgriLife Extension’s statewide integrated pest management coordinator and associate department head for the Texas A&M Department of Entomology, recommends do-it-yourselfers spread granular pyrethroid insecticides as directed for use in armyworm control by the label.
Alternatively, you can have a lawn care service apply sprayable insecticides.
Tip three: Predicting future occurrences
Armyworm outbreaks are typically directly linked to rainfall. In irrigated lawns, consistent moisture and subsequent fresh grass growth could influence their numbers from spring to fall.
Kerns said lawns and neighborhoods that see armyworms in turfgrass each year should monitor their lawns more closely.
“Another effective method for detecting reoccurrences of fall armyworms in turf is to use the soap flush method,” Kerns said.
Mix 2-3 tablespoons of liquid dishwashing detergent into a gallon of water and pour the mixture over a 3-foot by 3-foot area. Within about a minute, the armyworms will move from the thatch to the surface for easy detection.
“They’re called fall armyworms, but outbreaks aren’t limited to the fall,” Kerns said. “Infestations may begin in June depending on where you are located in the state and the amount of spring rainfall encountered.”
They can be a random pest, and every year seems to be different when it comes to infestation sizes and locations.
“It’s best to just be aware of them, keep an eye on your lawn and act quickly if you see them in your turfgrass,” he said.
