Signs that suggest that a lawn is infested with grubs are brown grass that pulls up easily, which indicates grubs are eating the roots of the grass, or the presence of skunks or raccoons searching for grubs to eat. Whether the lawn requires treatment depends on the level of infestation.
White grubs are the larvae of Japanese, June or masked chafer beetles. These grubs are white with brownish heads.
Depending on the level of infestation, an infested lawn may or may not require treatment. A good way to check the level of infestation is to dig up a square foot of lawn and check the soil. If there are five or less grubs per square foot of soil, the lawn can likely withstand the infestation without treatment. However, if there are 10 or more grubs, then the lawn should be treated.