White grub is the common name for larvae of scarab beetles like Japanese beetle, chafers and May/June beetles. White grubs feed on roots of grasses and can do considerable damage to turf grass. Because white grub larvae consume dirt along with plant roots their digestive track (visible from the outside) is usually packed at the back end with soil particles (see photo below).
White Grub Larva Photo by Steven Katovich,
USDA Forest Service, www.forestryimages.org
Professional turf managers, like golf course superintendents, generally use conventional insecticides such as imidacloprid to manage white grub populations. Homeowners can use less toxic materials because their tolerance for white grub damage is usually higher. Milky spore (milky disease) and entomopathogenic nematodes are two least-toxic choices.
See this article about biology and control of white grubs for additional information.