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(Article for October 2020)
Tropical sod webworms are out in biblical proportions this year. If you have brown patches popping up in your lawn, the sod webworm is the most likely culprit.
Tropical sod webworms are the larva of a small, dingy brown moth. The moths lay their eggs in lawns, pastures, and sports fields; then the eggs hatch into small caterpillars that feed on the grass. Sod webworms have favorite grasses. They tend to be worse in St. Augustine and carpet grass but will eat any turf grass.
The easiest way to tell if you have sod webworms is to dig around in the brown patch until you find worm sign. Chewed up blades of grass are a telltale sign. You may also find small piles of tan, sand like worm excrement. If you continue to dig around, you may find a worm. I typically find the worms along the edge of the brown patches. Sod webworms are night feeders, so they huddle close to the soil line during the day.
Once you have determined you have tropical sod webworms you can treat your lawn with a product containing bifenthrin (HiYield Bug Blaster and others). The liquid formulations will provide the best coverage. Treat the infected areas and spray a 3-4 foot buffer around the brown patches. Spray again in 7 days to kill any newly hatched worms.
Sod webworms are destructive pests of turf grass and pastures but do not usually cause permanent harm. Water your lawn during periods of drought and it should recover just fine.
Jessie Hoover is a County Agent with the LSU AgCenter covering horticulture in East Feliciana, West Feliciana, and St. Helena parishes. For more information on these or related topics contact Jessie at 225-683-3101 or visit www.lsuagcenter.com.
Tropical sod webworm.
Large brown patches in lawn caused by tropical sod webworm feeding.
This blade of grass has been eaten by tropical sod webworms.
The LSU AgCenter and the LSU College of Agriculture