**Lawn Grubs** is a collective term for the larvae of several species of beetles (primarily family Scarabaeidae, often called Scarabs or May/June Beetles, and Japanese Beetles). These creamy-white, C-shaped grubs live underground and are severe, economically significant pests of **turfgrass**. They feed voraciously on the root system of the grass, severing the roots from the plant. This feeding causes the turf to yellow, brown, and eventually die, leading to large dead patches that are easily rolled up like a rug.
Taxonomy and Classification
Lawn Grubs belong to the order Coleoptera. They undergo complete metamorphosis. The most damaging species in North America include the Japanese Beetle (*Popillia japonica*) and the European Chafer (*Rhizotrogus majalis*). Grubs are characterized by their C-shape, segmented body, three pairs of thoracic legs, and their slow, clumsy movement through the soil. The life cycle usually lasts one or two years, with peak feeding and damage occurring in late summer and early fall.
Physical Description
Grubs range from 1/2 to 1 inch long when mature.
- **Appearance (Key ID):** White or creamy-white, soft body; distinct brown head capsule; three pairs of legs near the head; and a large, swollen posterior end (often appearing dark due to ingested soil). They are typically curled into a “C” shape when dug up.
- **Habitat:** Found underground, usually in the top 2 to 4 inches of the soil profile, feeding directly on grass roots.
- **Damage Sign (Key ID):** Irregular patches of turf turn brown and die. The damaged turf can be easily pulled up from the soil because the roots have been severed. The presence of secondary damage from predators (e.g., raccoons, skunks) digging for the grubs is another tell-tale sign.
Distribution and Habitat
Lawn Grubs are common pests in temperate regions globally, particularly in areas with managed turf (lawns, golf courses). They prefer well-irrigated, lush turf for egg laying and larval development.
Behavior and Conflict
The conflict is significant turf destruction and landscape devaluation.
- **Root Severing:** Their feeding destroys the root system, causing the grass to die. This damage is often mistaken for drought stress until the turf starts lifting.
- **Secondary Damage:** The grubs are a high-protein food source, attracting nuisance predators like skunks, moles, and raccoons, which tear up the lawn while foraging for the grubs.
- **Timing:** The most severe damage occurs from August through October as the grubs grow large and prepare to overwinter.
Management and Prevention
Control is integrated pest management (IPM), relying on precise timing of insecticides or biological agents.
- **Scouting:** Dig up small sections of turf to check the grub density (typically 10 or more grubs per square foot warrants treatment).
- **Preventative:** Apply a systemic insecticide in spring/early summer to kill the newly hatched larvae before feeding begins.
- **Curative:** Apply a fast-acting contact insecticide in late summer or fall when damage is noticed. Requires immediate irrigation to move the product into the root zone.
- Apply **Entomopathogenic Nematodes** (microscopic worms) or **Milky Spore** (*Paenibacillus popilliae* for Japanese Beetles) to the soil. These require specific temperature/moisture conditions to be effective.
Conservation and Research
Lawn Grubs are managed as severe turfgrass pests. Research focuses on developing more effective strains of biological controls (nematodes, fungi) and improving the timing and efficacy of chemical applications to reduce environmental impact.