These grubs take just one year to complete each life cycle. The adult beetles are called masked chafers. They are slightly smaller than Junebugs and tan or straw brown in color with a black stripe across the eyes and face. Adults deposit eggs in the top inch or two of soil. Small grubs hatch and begin feeding on grass roots.
Most damage occurs in late summer and early fall after grubs have reached the second larval stage.
Grubs move deeper in the soil to overwinter. As the soil temperatures warm in the spring they move up to the grass roots, feed for a short time, pupate, and merge as adult beetles to begin a new cycle. Feeding in the spring is not as destructive as it is in the fall and only requires an insecticidal treatment. Phyllophaga grubs require three years to complete their life cycle. Adults are active in the spring, usually from late May until early July.