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Skaggs: Keep on the lookout for grubs invading your lawn
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Now is an excellent time to prevent white grubs in turf. White grubs live in the soil and feed on the roots of turf. Most white grubs have a one-year lifecycle in Georgia.

Adult beetles lay eggs in late spring or early summer. The eggs hatch into grubs, which feed and grow through the summer and fall, then dig down to spend the winter deep in the soil.

They become active as the soil warms in the spring, and feed for a few days to a few weeks, depending on the species. They then turn into pupae before emerging as adult beetles to continue the cycle.

The white grub is plump and C-shaped with three pairs of legs. They are white or cream in color and have a distinct brown head. White grubs are the immature stage of beetles such as June, Japanese or other scarab ones.

White grubs damage turf by feeding on the roots during the summer and fall and, to a lesser extent, in the spring before pupation. Very dry conditions can reduce survival of both eggs and small grubs. This seems to have happened across North Georgia last summer.

Adult flights have been much smaller than usual in most places in North Georgia. Beetle flights in the southern part of the state have been very heavy this summer, so grub populations in turf may be unusually heavy in the coming year.

Symptoms of white grub damage are similar to other factors that damage the root system: disease, soil compaction, poor fertility or drought.

Except for the green June beetle, grubs never come to the surface until they become adults. The only way to tell if a lawn is infested is to dig the grubs up.

To scout for white grubs, cut three sides of a one-foot square of turf and lay the grass back like a carpet. Dig gently in the soil to a depth of 4 inches and count the grubs you see. It is important to identify the grubs before you treat. The potential for turf damage is dependent on the number and type of white grubs present.

In general, insecticide treatment of white grubs is necessary if 10 or more grubs are found in one square foot of nonirrigated turf, or if 20 or more are found in a square foot of irrigated turf.

While it is easy to find white grubs in late summer when they are large and easy to see, now is not the ideal time to treat. Treatments are more effective if applied while grubs are small.

In most of Georgia, this means application in June or early July for best control. Once white grubs get bigger, there are fewer effective options, and higher pesticide rates will be required.

Good soil moisture and watering in the pesticide are also important for white grub control.

Several products are available for white grub control including Bayer Advanced, Merit, Sevin and Scotts GrubEx.

Billy Skaggs is an agricultural agent and Hall County Extension Coordinator. Phone: 770-531-6988. Fax: 770-531-3994.