Dealing with a Severe Grub Infestation in a New Lawn

Understanding White Grubs

White grubs are the most destructive insect pests in lawns. These C-shaped, whitish larvae are the immature stage of various beetles, including the annual white grub (tan chafer beetle), Japanese beetle, and May/June beetles. They feed on grass roots, causing turf to brown and lift like a carpet.

Life Cycle and Damage Timing

Annual white grubs lay eggs in mid-summer in well-watered, sunny lawns. Damage typically appears from mid-August through early October. Other species, like the true white grub, have a three-year cycle and can cause damage throughout the season. Japanese beetle grubs follow a similar schedule to annual white grubs.

Identifying a Grub Problem

Peel back sod in damaged areas and inspect the root zone. A population of 8–12 grubs per square foot warrants control. Lower numbers may not harm grass but can attract skunks and raccoons, which tear up turf searching for grubs.

Insecticide Options and Application Timing

Homeowner-available insecticides include trichlorfon (Dylox), bendiocarb (Intercept), halofenozide (GrubEx), and imidacloprid (Merit). Nematodes (Heterorhabditis bacteriophora) offer a biological alternative. Critical: Apply preventive products like imidacloprid or halofenozide in July before eggs hatch. Curative treatments in late September (as you did) are often too late because grubs have matured and descended deeper into the soil.

Spring Treatment Is Not Recommended

Spring applications are ineffective because grubs feed briefly and are near maturity. Turf is actively growing then and rarely shows damage.

Renovation vs. Recovery

Depending on grass type and infestation severity, the lawn may recover next spring. Wait and assess before committing to costly renovation. If renovation is needed, early fall is the optimal time.