Pestipedia

Turf Grubs

**Turf Grubs** (referring to the larval stage of Scarab beetles, primarily **Japanese Beetles**—*Popillia japonica*, **European Chafers**—*Rhizotrogus majalis*, or **Masked Chafers**—*Cyclocephala* species) are white, C-shaped grubs that are major pests of **turfgrass and lawns**. The conflict is severe root destruction: the grubs live in the soil and chew off grass roots, preventing the turf from absorbing water and nutrients. This results in **large, irregular dead patches** of turf that can be lifted up like a carpet, leading to widespread lawn replacement costs and secondary damage from predators (skunks, raccoons) digging for the grubs.

Taxonomy and Classification

Turf Grubs belong to the order Coleoptera (Beetles), family Scarabaeidae. They undergo complete metamorphosis. The larval stage is the primary pest, spending most of the year underground before pupating and emerging as an adult beetle.

Physical Description

Larvae are medium-sized, 1/2 to 1 inch long.

  • **Larva (Key ID):** Plump, soft-bodied, creamy-white grubs that are typically curled into a distinct **”C” shape**. They have three pairs of thoracic legs. Identification often requires examining the unique hair pattern on the posterior tip (raster).
  • **Adult Beetles:** Variable (e.g., shiny green and copper Japanese Beetles, or uniformly light brown chafers).
  • **Damage Sign (Key ID):**
    • **Loose Turf:** Patches of grass that pull up easily with no roots attached.
    • **Predator Digging:** Damage from skunks, raccoons, or birds tearing up the lawn to eat the grubs.
    • **Thinning/Yellowing:** Grass that appears drought-stressed, even when watered.
  • **Conflict:** Severe root destruction and lawn loss.

Distribution and Habitat

Turf Grubs are widespread globally. Their habitat is the root zone (top 2-6 inches) of turfgrass.

Behavior and Conflict

The conflict is density and soil-level damage.

  • **Economic Threshold:** Control is necessary when grub populations exceed 8-10 grubs per square foot.
  • **Timing:** The most severe damage occurs in late summer and fall, when the grubs are large and actively feeding before overwintering.

Management and Prevention

Control is integrated pest management (IPM), utilizing biological controls and targeted insecticides.

  • **Biological Control (Key):**
    • **Nematodes:** Apply entomopathogenic nematodes (*Heterorhabditis bacteriophora* or *Steinernema* species) when the grubs are young (mid-summer) and the soil is moist.
    • **Milky Spore:** Apply *Paenibacillus popilliae* (Milky Spore) for long-term (multi-year) suppression of Japanese Beetle grubs.
  • **Chemical Control:**
    • **Preventative:** Apply a long-residual insecticide (e.g., containing chlorantraniliprole) in June/July to kill newly hatched grubs.
    • **Curative:** Apply a faster-acting insecticide in late summer when high populations are actively causing damage.

    • Conservation and Research

    Turf Grubs are managed as high-priority turfgrass pests. Research focuses on host-plant resistance in turf cultivars, improving the efficacy of biological agents, and developing better monitoring methods for predicting outbreaks.