There are several types of white grubs that feed on the roots of lawn grasses. All of them can cause severe damage if left untreated.
Grubs live and feed in the soil. It's easy to miss them as they gradually cut the roots out from under your lawn until brown patches begin to appear and they're finally discovered. If you suspect grubs, pull back the turf. If the lawn pulls up easily (like new sod), you may find white grubs in the top inch or so of the soil.
Grubs are the larval (or worm) state of many types of beetles. The beetles lay their eggs in your lawn, and the newly hatched worms work their way through the thatch and into the soil, where they feed on the roots of grass plants. Most beetles lay their eggs in mid to late summer, and the young grubs do their greatest damage during the fall months.
As the weather cools, most grubs burrow deeper into the soil for the winter. They then return to the surface to feed again as the soil warms in the spring. After this spring feeding, the grubs pupate into adult beetles and begin the cycle again.
Grubs don't disappear on their own. They should be treated by Turf Care before damage begins to appear, or as soon as they're discovered. When discovered early enough in the year, a preventative treatment can be applied. When damage appears in the fall, a fast-acting curative treatment will be needed.