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Yale Park Homeowners Association

Texas AgriLife Extension Service

Kimberly Schofield
Program Specialist-Urban IPM

White Grubs Destined To Destroy Turfgrass

There are two important white grub species that infest turfgrass in Texas : the June beetle, Phyllophaga crinita and the southern masked chafer, Cyclocephala lurida.  Both species of grub worms feed mainly on roots of turfgrass, causing the turfgrass to become brown and easily removed in large clumps.  White grubs pose the most damage to lawns during the summer and fall, when the larger grubs begin to feed.

Both species of grub worms require one year for development from egg stage to adult stage.  After mating, the females will lay their eggs in the soil.  The eggs will hatch into small white grub larvae.  These developing white grubs will feed on roots of turfgrass and continue to cause more damage in the mid-summer to late fall.

White grub damage can be determined by the presence of irregular shaped areas of weakened or dying turfgrass.  By detecting white grubs early, treatments can be applied before serious root damage occurs.  Also, treatments are more effective when applied to smaller grubs.

Before treating with insecticides, lawns must be inspected in several areas.  Insecticides should only be applied if a grub worm infestation exists in your lawn, since unnecessary use of insecticides can cause insect resistance.  Also applied insecticides do not discriminate between beneficial insects and pest insects, so many beneficial insects could be killed as a result of unnecessary application.

In order to inspect an area, soil sections should be taken randomly in areas that are at least 3 to 4 inches deep and the sampled sections should equal one square foot for every 1000 square feet that is infested.  One square foot can be sampled by removing four, 6 inch square pieces of turf or ten, 4 inch cup cutter core samples.  If more than 5 white grubs are found within this square foot, then treatment should be applied.

The optimal time for inspection and for treatment application should be 5 to 6 weeks after the heaviest June beetle flights are seen.  Timing of application is due to both non-chemical and chemical control options being more effective at controlling smaller grub worms, less than ½ inches.  For the DFW metroplex, treatment in late July to early August is optimal.  However flight periods may vary from year to year, due to rainfall variations.

Treatment Options:

Non-Chemical Control Options:
Several non-chemical treatments are available for controlling white grubs.  Beneficial nematodes within the genera Steinernema and Heterorhabditis attack white grubs and other soil inhabiting insects.  Nematodes can be purchased in stores or through garden supply catalogs.  One-quarter inch of water should be applied before and after nematodes have been sprayed onto the lawn.  This will allow the nematodes to contact white grubs in the soil.

Chemical Control Options:
There are several chemicals on the market including systemic insecticides such as imidacloprid and clothianidin.  These products should be applied before extensive grub worm damage is seen.  Irrigating the soil prior to application can improve effectiveness of the insecticides.  For dry soils, ¼ to ½ inches of water should be applied to promote the grubs to move closer to the soil surface and allow the insecticides to penetrate through the soil.  Also water should be applied after treating to allow the insecticide to reach the root zone.  If using a liquid insecticide, ½ to 1 inch of water should be applied.  If using a granular insecticide, water should be supplied within 24 hours.  Application of water should occur slowly, in order to avoid runoff.

White Grubs
(Coleoptera: Scarabaeidae), June beetle larvae.
Photo by Dr. Bart Drees.

Mention of commercial products is for educational purposes only and does not represent endorsement by Texas AgriLife Extension or The Texas A&M University System.  Insecticide label registrations are subject to change, and changes may have occurred since this publication was printed.  The pesticide user is always responsible for applying products in accordance with label directions.  Always read and carefully follow the instructions on the container label.

Email Mark Solomon Link to www.Assurnet.biz website

Email Abby Miller Link to www.FathomRealty.com website

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