White grubs

C-shaped, soft, white-bodied larvae with tan heads and three pairs of legs, found in the soil-thatch interface beneath turf and identified to species by the raster pattern of bristles on the underside of the tip of the abdomen. They are the larvae of scarab beetles — Japanese beetle, masked chafers, May/June beetles, and green June beetle — and are detected by cutting and peeling back sod to count grubs per square foot.

Irregular patches of wilting, yellowing turf that brown and die and can be rolled back like loose carpet because the roots have been chewed off; injury looks like drought that does not respond to watering, and secondary digging by skunks, raccoons, and birds searching for grubs tears up the weakened sod.

Most damaging species (Japanese beetle, masked chafers, green June beetle) have a one-year life cycle. Adults fly and lay eggs in early-to-midsummer (roughly late June through July); eggs hatch and grubs feed on roots through three instars from midsummer into autumn, then move deeper to overwinter, return to feed briefly in spring, pupate in late spring, and emerge as adults the following summer. May/June beetles take two to three years per generation.

Root-feeding damage is heaviest in late summer and early fall when large third-instar grubs feed near the surface, and again to a lesser degree in spring. Egg-laying and survival are favored by moist soil, so irrigated and well-watered turf in mid-to-late summer is especially attractive; damage often shows first on slopes and sunny, drought-prone areas.