One More Time What To Do About Grubs In The Soil
by Art Drysdale
by Art Drysdale


Art Drysdale, a life-long resident of Toronto and a horticulturist well known all across Canada, is now a resident of Parksville, British Columbia on Vancouver Island, just north of Nanaimo. He has reno-vated an old home and has a new garden there. His radio gardening vignettes are heard in south-western Ontario over radio station Easy 101 FM out of Tillsonburg at 2 PM weekdays.

Art also has his own website at

August 29, 1999

Having written about the new grub control product, Merit, just a month ago, I hesitated to devote another whole column to the control of white grubs this soon. However, grub-infested lawns is one of the most common problem homeowners have, and thus I decided to discuss the subject here one more time this year! Now is the optimum time for the application of a chemical to kill white grubs since the young voracious grubs have just gotten started in the soil.

White grubs of at least three insects chew at the roots of turf and may easily cause it to die. They are also a favoured food of raccoons and squirrels, and these rodents then move in and often dig up the infested turf, leaving it looking like a plowed field. Chinch bugs, on the other hand, are not in the soil, but above it, and eat the stems of the grass plants around the thatch layer. These insects can easily kill an entire large lawn in the matter of two or three days if the infestation is severe. For homeowners with lawns infested either with white grubs or chinch bugs there are still just two chemicals available to solve the problem.

As mentioned a month ago, the new product Merit will likely do the best job of the three available, but it is NOT available for domestic users. It is only sold to professional applicators who take a special course.

There is still another "new" chemical available this year - Sevin XLR Plus--but it too, is only available to professional applicators. Now Sevin (also known as Carbaryl) is anything but new. However, this formulation (extra long residual) was newly registered in Canada just recently. While it is now too late for the use of Merit, if you use a professional lawn care applicator, such as Weed Man or ChemLawn, you might want to ask them about Sevin XLR Plus. It can, and should be put on right now.

Finally in the realm of treatments for white grubs, there is another new chemical on the horizon. Registration has been requested in Canada, but it might well be next year at this time at least, before it is cleared for use. Its name if Mach II, and it comes from the Rohm & Haas company.

Meanwhile, for homeowners with grub and chinch bug problems, who want to do the treatment themselves, you are still limited to Chlorpyrifos, and Diazinon. If you think you have a white grub problem, it’s best to check it out and make certain.

The best way to gauge whether you have an excessive number of grubs in your garden (they also attack the roots of a number of other plants), is to dig an area say 30 cm (1’) square in a number of different locations of the garden. You should certainly include at least one such peeling back of the turf in both the front and back lawn. You need not go deep. Currently the grubs are being reported near the soil surface (5 cm or two inches). If you find less than eight or ten grubs in such an area, you likely don’t have to worry. But, if you find more, then you will definitely have a problem.

If you do find an excessive number of grubs, it is best to apply Diazinon--the only chemical available to you that works well [70 percent control vs. only 40 percent for Chlorpyrifos in University of Guelph tests]. However, to work well, it should be applied on a well-wetted lawn (watered immediately in advance for at least an hour), and then watered for the same amount of time right after the application.

Now, if you don’t have a hose-end applicator (such as a Dial-a-spray), there is a new, simple way to apply this control. At least two manufacturers have a ready-to-spray format that you simply hook up to the hose, turn the safety control, and the hose will apply just the right amount--no mixing and no mess! By the way, the ideal time to apply a grub control such as this is during a rainfall, when the watering before, and after is taken care of for you by Mother Nature! I’ve even been known to be out spraying with a hose-end in the middle of a rainfall, wearing a raincoat!

I cannot emphasize enough that if you have this digging or rolling-back of the turf problem this autumn (caused by raccoons, squirrels or skunks) you are almost sure to have it again next spring--unless you treat the area, following the foregoing guidelines--immediately. I should stress that you must get the chemical on NOW. By late September the grubs will start to go deeper in the soil for the winter. Once they do that, you will have wasted your time and the chemical because it will not reach them. And, you will have the same problem come spring.

By Art C. Drysdale, 6 Nesbitt Drive, Toronto, Ontario M4W 2G3Art Drysdale is seen hourly every day on Canadas Weather Network at 23 minutes after the hour, and heard Saturdays from 9 to 11 am, with a live two-hour radio broadcast on Toronto's TALK640 (640 on the AM dial)

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