What are grubs? Can they damage my lawn? When do I protect my lawn? NOW!

White grubs, sometimes called grubworms, are small, white, C-shaped larvae of a group of beetles known as scarabs. The most common grubs that we encounter in lawn care are: Japanese beetles, northern and southern masked chafers, European chafers, Oriental beetles and Phyllophaga (May-June beetles).

White grubs feed on the roots of plants. The first sign of damage is that the grass wilts easily despite watering. Damage symptoms mimic drought stress.

feeding will cause the turf to die in irregular patches. The turf will feel spongy underfoot and birds may begin to feed in the area. With heavy infestations, the turf can be rolled back like a carpet. Animals, such as raccoons, skunks and moles, may tear up the turf while looking for grubs and other insects.

Occurrence

White grubs attack all the cool season and transition zone turfgrasses. Masked chafers and Phyllophaga occur throughout the United States. Japanese beetles occur primarily in states east of

the Mississippi river; however, localized infestations have been found in plains and western states. The European chafer and the Oriental beetles are found mainly in the Northeast and in the

Great Lakes region.

Description

Most white grubs develop from egg to adult in one year. Adults lay eggs in late spring to early summer. The eggs hatch within 10-14 days as long as there is adequate soil moisture. Grubs feed throughout the summer and fall. Cool soil temperatures in the fall force the grubs to go down deep into the soil to survive the winter. The grubs return to the surface in the spring. Japanese beetle and European chafer grubs may feed and cause some damage in the spring. All pupate in the spring and the new adults emerge 6-10 weeks later.

Phyllophaga beetles (May- June beetles) take several years to develop from eggs to adults. The adults emerge in early spring and begin to lay eggs. The larvae may feed for 2 or 3 summers before pupating.

Control

Because white grubs live below the thatch layer in the soil, grubs are somewhat difficult to control. The typical method is to apply a pesticide as close to egg hatch as possible to control young first instar grubs. The timing of this varies across the country but typically occurs from late-May to mid-August. Because the grubs reside in the root zone, the treatment should be watered in to move the pesticide into the target area. Once the grubs are actively feeding, a curative application may be warranted. In this case, a product that moves quickly through the thatch and into the root zone is desirable. High populations of white grubs (Japanese beetles or European chafers) may cause significant turf damage in the spring of the year. It is difficult to control grubs in the spring because they are large and the window of treatment opportunity is short.