New Treatment Approaches for White Grubs
By Nathan Riggs, Extension Agent - IPM -Texas Cooperative Extension, Bexar County

June Beetles (June Bugs) and white grubs are traditionally one of the most common enemies of the St. Augustine lawn in San Antonio. Normally, the June Beetle does not feed on anything (except the leaves of some species of Oaks) and lives only to mate. The larvae, or white grubs, of the June Beetle are the troublemakers. They feed on the roots of grasses and cause significant damage or even death to infested turf.

Over the years, the most common treatment method for white grubs has involved a combination of vigilance followed by treatment. Homeowners would watch for the beetles and then wait 4 to 6 weeks before granular insecticides to the lawn and watering them in. Others would find an infested area, cut out a square-foot section and count the grubs underneath. Finding 5 or more grubs would warrant an insecticide application. The chemicals in these liquid and granular insecticides are classified as broad-spectrum insecticides - in other words they kill nearly every insect they contact. This method still works fine for those who employ it in their lawns. There are also beneficial nematodes than can be applied to the lawn that will seek out and attack the grubs. These nematodes are most successful when the soil remains moist and doesn't become too dry. In San Antonio, keeping beneficial nematodes alive in the lawn requires irrigation 2 to 3 times per week. Father Time has brought new treatment strategies that homeowners can implement against the dreaded C-shaped menaces in their turf.
There are at least 3 new products on the market to battle white grub infestations in home lawns. Each of these products contains a relatively new chemical active ingredient that behaves much differently than Dursban™ or diazinon in the past. The biggest benefit of all of these new products is that they can be applied BEFORE the June Beetles appear. Yes, all of these can be applied as preventative measures! How does this work? These products are taken up into the grass and act systemically. When the white grubs feed on the grass roots, the chemicals kill them. These products are target-specific in that they only kill insects that feed on the grass. Novel, huh? Another nice piece of this puzzle is that the active ingredients are much friendlier to mammals, birds, and non-target insects than the old mainstays.

OK, what are these products and how are they applied? Grub-Ex by Scotts^®, Advanced Lawn™ Season-Long Grub Control by Bayer, and Merit^® by Bayer are some of the products available to apply on the lawn for season-long grub control. They are sold at local nurseries, garden centers, and large retail home improvement stores. The best time to apply any of these products is mid-April and then any time until August. Applying the products in mid-April is advertised to give season-long control with one application. Too good to be true? These active ingredients have been proven in many other products that have had much success. Time will tell whether or not they will prove themselves as worthy allies in the war on white grubs.
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This page last modified on: May 1, 2002