Lawn grubs are beetle larvae that live in the soil under your grass. They are fleshy, crescent-shaped creatures that eat grass roots, resulting in large areas of dead lawn. Not only do the grubs themselves damage your lawn, leaving large brown spots no matter how diligently you water your grass, but they attract skunks, moles and raccoons and an assortment of other unwanted garden pests who wreak havoc on your yard trying to get to the grubs.
Push the edge of a shovel into three sides of a 1-foot square of dying brown grass and lift up the flap of turf. If you feel no resistance, grubs have likely eaten the grass roots. More than five grubs under the 1-foot square indicates a grub infestation serious enough to call for eradication measures, according to the Penn State College of Agricultural Science.
Apply a powdered formulation of the bacteria Bacillus popilliae to your lawn. This bacteria causes milky spore disease in Japanese beetle grubs, which kills these pests. Sprinkle 1 tsp. of the bacteria powder over sections of lawn in a checkered pattern and water it in thoroughly.
Spray beneficial nematodes over your lawn. Nematodes are microscopic worms that kill grubs by feeding on them from the inside. Available at many gardening stores, nematodes are safe for pets, people and the majority of insects.
Mow your grass so that it remains at least 2 inches long. Japanese beetles, the species responsible for much grub damage to lawns, do not like to lay their eggs in long grass.
Water your grass once every three days instead of every day. This watering schedule is less conducive to grubs, which need a constant source of moisture to survive, and makes it less likely that beetle eggs will hatch.