Writer: Mary Porter, (972) 952-9232, m-porter@tamu.edu
Contact: Dr. Mike Merchant, (972) 952-9204, m-merchant@tamu.edu
DALLAS - To avoid a long and difficult battle with white grubs, treat lawns in early to mid-August in North Texas, according to Texas A&M entomologists.
“The earlier you treat in August, the better,” said Dr. Robert Crocker, entomology researcher at the Texas A&M Agricultural Research and Extension Center in Dallas.
“You want to treat while the grubs are small. We estimate the best treatment window this year is between Aug. 1 and 20. Mating flights of June beetles (the adult stage of white grubs) predict when grubs will attack your lawn. These flights occurred over two peaks in mid-June. Computer models and field sampling calculate that now is your best chance to treat lawns known to have white grub problems.”
The Texas Agricultural Extension Service recommends checking for grubs before deciding to treat. Dig small holes, three to four inches deep, in several places around the yard.
Grubs found during this target treatment period should be small, less than the length of a thumbnail. They are C-shaped, whitish, worm-like insects that feed in the grass root zone. Treatment is necessary only when more than four or five grubs are found per square foot of turf.
“Not everyone needs to treat,” cautions Dr. Mike Merchant, Extension urban entomologist. “Most homeowners don’t have grub infestations serious enough to treat. But if you’ve had problems with grubs in the past and find high numbers in your lawn, you will want to treat now for the best control.”
Not all brown spots in lawns are caused by insects. Lack of water and some turfgrass diseases also cause dead spots. To be sure, try tugging at the grass in the brown area. If the grass pulls out with no roots attached, or if you can lift entire sections of turf from the soil, you may have grubs and want to apply a pesticide.
White grubs hatch from the eggs of June beetles in North Texas as their name indicates, in June. Four to six weeks after the major mating flight is the best time to treat.
“Gardeners who wait too long to treat, after Aug. 20 this year, risk a struggle with the older and more pesticide-tolerant grubs,” warned Merchant. “The bigger they grow, the more damage they do.
“When using any pesticide, read and follow labels carefully. Overuse or misuse of insecticides can cause pollution and lead to poor control of the grubs.”
A fact sheet, White Grubs in Texas Turfgrass (L-1131), is available on the Internet at http://agpublications.tamu.edu/pubs/eentom/l1131.pdf or through county Extension offices.
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