White grubs are the immature stage of beetles.
Depending on the species, they can live in the soil for up to three years before maturing into the adult beetle. Grubs have a white body with six legs and a dark head. Not all grubs will eat Fraser fir roots. Some, such as the Japanese beetle grubs, only eat grass roots. Others, such as the Green June beetle grubs, only eat dead organic matter on the surface of the soil at night.