White Grub Season is Here

This is the time of year when annual white grubs begin to infest turfgrass and, in the Midwest, we are blessed with an assortment of different annual white grub species. This group of insects produces one generation each year with the adults becoming active by early June. Adults lay eggs in turf and 1st instar larvae are usually present and feeding in the root zone by early July. By early August, 2nd instar larvae are usually present and 3rd instar larvae may be present by the end of August. Most damage to turf is associated with feeding by 3rd instar larvae and this is the overwintering stage. In some cases, especially where European chafer is present, damage may also occur the following spring.

Management of white grubs should be based on previous history as well as the functional and aesthetic characteristics of the site. On high maintenance turf, tolerance for damage may be low and a preventive white grub management approach may be warranted. Conversely, minor damage to low maintenance turf may require no remediation at all aside from adequate moisture and fertility to help the turf recover. The chart below represents the relative efficacy of all white grub insecticides labeled for use in turf in relation to application timing.

The chart is intended to help turfgrass managers understand the insecticide choices available to them and help them make the best white grub control decisions at any given point in the growing season. Insecticide products that do not contain one of the active ingredients (chemical names) listed on this chart will not usually provide good grub control. Keep in mind that the active ingredients listed on the left side of the chart may be formulated and distributed under various trade names aside from those listed on the right. As always, remember to read and follow directions on the label of any insecticide product.

Doug Richmond
Associate Professor and Turfgrass Entomology Extension Specialist
drichmond@purdue.edu

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