White Grub

White grubs are the soil-dwelling larvae of scarab beetles, most commonly species in the genus Phyllophaga, known as May beetles or June bugs, though the term is also applied loosely to the similar-looking larvae of Japanese beetles, chafers, and other related scarabs. They spend the vast majority of their lifespan underground, curled into a characteristic C-shape as they feed on the roots of grasses and other plants.

Though largely unseen, white grubs are ecologically significant soil organisms, contributing to soil aeration and nutrient cycling as they burrow and feed. In lawns and turf, dense populations of white grubs are sometimes noted as a garden or lawn pest because root feeding can affect the vigor of grass, but the grubs themselves are a normal part of the below-ground food web and an important food source for moles, skunks, birds, and other grub-eating wildlife.

• Soft, pale white to grayish body curled into a distinctive C-shape
• Brown to reddish-brown hardened head capsule
• Three pairs of short, well-developed legs near the front of the body
• Body appears wrinkled and segmented, tapering slightly toward the rear
• No wings or eyes visible, consistent with a subterranean larval stage
• Distinguished from other soil grubs by the raster pattern (arrangement of hairs and spines) on the underside of the last abdominal segment, used by specialists to identify species

Found in soil beneath lawns, pastures, golf courses, and gardens across much of North America, wherever grass and turf roots provide a food source. White grubs live several centimeters below the surface, moving deeper in winter to escape freezing temperatures and closer to the surface in the root zone during the warmer growing season.

White grubs feed primarily on the roots of grasses and other plants, chewing through root systems as they move through the soil, which is the basis for their occasional status as a lawn and turf pest. They spend almost their entire larval life underground, rarely if ever surfacing, and adjust their depth in the soil profile seasonally in response to temperature. As soil organisms, their tunneling contributes to aeration and organic matter turnover, and they represent an important food resource for a range of predators, including skunks, moles, raccoons, and ground-foraging birds.

Adult beetles lay eggs in the soil in late spring or early summer, and the eggs hatch into first-instar grubs that feed on fine roots and organic matter near the surface. Grubs pass through three instars over one to three years depending on species and region, growing progressively larger and moving deeper into the soil to overwinter each year before completing development. In their final season, mature grubs form a pupal cell in the soil, transforming into adult beetles that emerge from the ground, typically in late spring, to mate and begin the cycle again.