The larvae of several beetle species, commonly know as white grubs, are major pests of Canadian turfgrass. In Ontario the most common white grub species are the European chafer and the Japanese beetle. Injury to turfgrass occurs from larval munching on the roots, resulting in infested areas first turning yellow, then brown, and finally dying. When grub populations are heavy, areas of turf can be easily lifted from the soil. In addition, moles, raccoons, skunks, birds and other vertebrate animals feed on white grubs. Turf can be heavily damaged by the activities of these animals as they forage for grubs in infested turf. I have seen an entire lawn vanish in a matter of 2 weeks.

The adult beetle stage of white grubs differ in size, colour markings and life cycle, while the larval stage is similar in appearance and can be characterized by the C-shaped position when found in the soil-thatch interface area of the turf. Egg laying can occur at various times during the season depending on species and region of the country and environmental conditions, but usually begins in late June or early July and continues for four to six weeks.

In most cases, adult emergence occurs in mid-summer often after significant rainfall or irrigation, followed by mating; and egg laying. The eggs hatch and the small larvae begin feeding on turf roots, with molting from first to second instar occurring in a few weeks. Most of the feeding damage is done by the comparatively large third instar larvae, and it is this stage that causes visible turf damage. The following spring, these larvae will move up to the soil-thatch interface to feed and replenish food reserves lost during the winter months before moving back down and transforming in to the pupal stage. A one year cycle will be completed with beetles emerging from this pupal stage a short time later.

In order to maintain high quality turf, it may not be possible or logical to wait for damage to occur before control options are implemented. Therefore instead of waiting for the pest problem to occur, which may require higher pesticide rates for curative action, a preventative program would be most effective.

MERIT provides season long grub control with 90% plus results. Grub control with merit is achieved at very low rates—requires 6 to 22 times less active ingredient than other grub products. Merit is more effective than any other grub product currently registered in Ontario for turf grass.

A number of factors including application timing, uniform and accurate application, amount of thatch, rainfall and/or irrigation following treatment, insects species, insect infestation level and dosage rate affect soil insecticide performance. These factors must be considered when treating with merit in order that optimal insect control is consistently achieved.

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