White grubs: Biology and ecology

True whit grub: Grubs have large, strong mandibles for chewing roots. (Photo Marlin E. Rice)True white grub: Grubs have large, strong mandibles for chewing roots. (Photo Marlin E. Rice)

True white grubs typically have life cycles that span 3-4 years (known as semivoltine) while the annual white grub is univoltine. These grubs are not common in soybean, but in infested fields, larvae can be found feeding on roots throughout the growing season. The adults fly to and feed on foliage of deciduous trees and, during spring, will drop to the ground to deposit eggs. Larvae will feed in the root zone just a few inches from the soil line. With the onset of winter the true white grub will migrate deep into the soil to overwinter as either a larva or a pupa (depending on its developmental stage).