White Grubs and What to do About Them

What do they look like?

White grubs, sometimes called grubworms or grubs, can vary in size from a few millimeters in length to close to 1 inch. Regardless of length, however, the shape and color are all similar. They have brown heads with large jaws, and plump, cream-colored bodies. The back part of their abdomen is often dark from ingesting roots and soil. They tend to take a C-shaped position, so if you see a mass of fat, white insects aligned like that letter, you've spotted grubs.

How do we know we've got them?

Early stages of grub damage appear mainly in the late summer or early fall when the plant begins to wilt. Watering does not make the stress go away, and because the grubs have decimated the roots, damaged turf can be picked or even rolled up with little effort. The turf will also feel spongy underneath. In addition to doing their own damage, grubs are an excellent food source for several animals, and these predators will harm the lawn as well while they are feeding. Since grub damage often goes undetected until the turf is rolled up by hungry predators, it is often too late to save the lawn from severe destruction.

How do they damage our lawns?

The grub feeds on the turfgrass roots. It chews the roots off close to the surface, preventing the plant from obtaining water and food. When the conditions are hot and dry, the damage from grubs is more apparent as the plant cannot recover. Damage during wet periods or from small infestations on healthy lawns can sometimes go unnoticed.

How do we get rid of them?

Be alert to sites that have lots of adult beetles in June and July. You should prepare for grub activity following in August and September. Like so many lawn pests, grubs are best controlled when they are young, right after they have hatched. The key to controlling them is knowing the beetle species and life cycle for your area. To do this, take a spade and dig up a 1 square-foot area of lawn at a depth of 3 inches. Spot-treating through scouting is essential to allow natural predators of grubs to proliferate. Do this when you know the grub is beginning to become active. Insecticides also can work well when used near the surface, and some can even provide season-long protection if timed correctly. Take note, however, that these treatments can be expensive, and must be professionally applied.

Watering during periods of grub feeding will encourage root growth, though sometimes it can mask damage symptoms. Heavy watering during late spring and early summer can be attractive to adult beetles as excellent places for their eggs to survive, so remember to determine the best watering strategy for your lawn, one that is neither too sparse, nor too heavy. Grubs also love heavily thatched areas, so control this through core cultivation. Overall, the best approach to grub control is to monitor and spot treat infected areas with insecticides at proper times. This is not only the most cost-effective, but helps keep beneficial predators on your side.