University of Georgia
You'd expect something that could destroy huge chunks of your lawn to look menacing and possess a suitably evil name. It's just hard to fear white grubs.
They need a better agent, because their looks (little C-shaped worms with creamy white abdomens and brown heads) are deceiving. When these things quietly munch away at grassroots, they can be deadly to your lawn.
And you can't even tell they're there.
"You have to check for them," said Will Hudson, a University of Georgia Cooperative Extension entomologist.
Even in heavy populations, he said, it takes a long time for small grubs to do damage. The symptoms are wilted or brown patches of turf. But that's not uncommon in late summer and early fall.
"Especially this year," Hudson said, "bad-looking grass can be due to hot, dry weather or other factors such as disease or poor fertility. The only way to tell for sure is to dig in and look."
White grubs are the larval stages of a number of beetles, he said, including green June beetles, chafers, May and June beetles and Japanese beetles.
To check your lawn for them, take a shovel and cut three sides of a square foot of lawn turf, Hudson said. Then fold that flap of sod back and look for grubs in the top 1 to 2 inches of soil and the grassroots.
"If the soil is dry," he said, "the grubs will be down deep, so be sure the soil moisture is good before you start."
If the number of grubs averages more than four per square foot, he said, you may need to apply an insecticide. To decide the best one to use, find out which species of grubs you have.
Your county UGA Extension agent can help you identify white grub species. Or get a leaflet, "White Grub Pests on Turfgrass," at the county Extension office or online (pubs.caes.uga.edu/caespubs/pubcd/l428-w.html).
For home lawns, Hudson said, the best insecticides to use are granulated formulations of imidacloprid (sold in the Bayer Advanced Season-Long Grub Control Granules, Scotts GrubEx Season-Long Grub Killer, etc.), or the growth regulator halofenazide (sold as Grub-B-Gon).
"Both of these products are effective on small grubs," he said. "As we get into the fall, they won't control the larger grubs as well. The only 'rescue' treatment labeled for home use is trichlorfon, which is sold as Dylox or Bayer Advanced 24-Hour Grub Killer Plus."
Whatever you use, he said, it's critical to water it in properly. If you don't, it's useless.
You have to get it to the roots, he said. Because they're in the soil, white grubs are hard to control anyway. If you don't get the insecticide down there where they are, you don't have a chance to get them.
"Avoid very hot times with bright sunlight, too," Hudson said. "For the best results, treat late in the afternoon."
(Dan Rahn is a news editor with the University of Georgia College of Agricultural and Environmental Sciences.)