If you are thinking Déjà vu when it comes to seeing moths flying around your lawn again, you are right. I have found a lawn in the Lafayette area that is under attack by Tropical Sod Webworms. Adult moths captured at this site were identified by LSU entomologist, Dr. Dennis Ring, as being Tropical Sod Webworms.
Moths you see flying do not feed on the grass blades, their offspring (caterpillars) do the damage. These moths can continuously fly into your yard from other areas at will. Moths do not have chewing mouthparts; rather it is like a straw. They feed on flower nectar and you may see them in shrubbery in your yard at times.
Once you begin to see numbers of moths in your yard, you can expect to have baby caterpillars within 7-10 days. Larvae can get up to 1 inch long and are light green to gray green with dark spots on their body. We could get 3 to 4 generations in a season.
This is the time to begin using insecticides to control the damage they cause. Before you make the first application, look at the blades of grass in your St. Augustine Grass to see if there appears chewed up margins. This will confirm that damage is beginning and that spraying should follow shortly thereafter.
Caterpillars can only chew into the leaf blade, the stolons are too tough for them to chew, and therefore sod that was healthy should be able to recover.
Dr. Ron Strahan with the LSU AgCenter recommends using several different insecticides to control this pest. Follow label directions carefully. Here is a list of products with their active ingredient.
Spinosad (an organic insecticide): Monterey Organic Garden Insect Spray; Fertilome Borer, Bagworm, Tent Caterpillar and Leafminer Spray; Green Light Spinosad Lawn and Garden Spray; Dow Spinosad Home and Garden; Success Naturalyte; Bonide Captain Jack’s Deadbug Brew and other brands.
Bifenthrin (a pyrethroid): Talstar; Bifenthrin; Ortho Home Defense and other brands.
Acephate (systemic): Acephate; Orthene and other brands
Carbaryl: Carbaryl, Sevin
By controlling these webworms early, you can save your yard from infestations of lawn weeds that will become another problem for you in the future.
Information by LSU Ag Center. Visit online here.