**Turf Webworms** (primarily referring to **Sod Webworms**—*Crambus* species, or **Tropical Sod Webworms**—*Herpetogramma* species) are the larvae (caterpillars) of small snout moths. They are major pests of warm- and cool-season **turfgrass and lawns**. The conflict is severe, localized lawn damage: the larvae chew off grass blades just above the soil line and often construct silk-lined tubes or **”webs”** in the thatch layer for protection. This causes irregular patches of brown, dead grass, mimicking drought stress or fungal disease, leading to significant repair costs.
Taxonomy and Classification
Turf Webworms belong to the order Lepidoptera (Moths and Butterflies), family Crambidae. They undergo complete metamorphosis. The larval stage is the highly destructive pest stage.
Physical Description
Adult Larvae are medium-sized, 1/2 to 1 inch long.
- **Larva (Key ID):** Gray, greenish, or brownish caterpillars with small, distinct **dark spots** or “pin-dots” over their body. They curl into a tight “C” shape when disturbed.
- **Adult Moth (Key ID):** Small, slender, buff-colored moths that fly erratically over the lawn at dusk, resting with their wings tightly folded around their body (snout-like appearance).
- **Damage Sign (Key ID):**
- **Dead Patches:** Irregular, small, brown, dying patches of grass, often growing larger.
- **Silk Webbing:** Silken tubes, tunnels, or mats visible in the thatch layer near the soil line.
- **Flushing:** Larvae will often rise to the surface if an irritant (e.g., soapy water) is poured onto the turf.
- **Conflict:** Lawn destruction and aesthetic loss.
Distribution and Habitat
Turf Webworms are widespread globally. Their habitat is the thatch layer and soil surface of lawns, where they feed primarily at night.
Behavior and Conflict
The conflict is difficult detection and high potential for rebound.
- **Hidden Feeding:** They feed at night and hide in the thatch during the day, making them difficult to detect until damage is severe.
- **Rapid Generations:** Many species have multiple generations per year, leading to rapid reinfestation if control is incomplete.
Management and Prevention
Control is integrated pest management (IPM), utilizing monitoring and targeted treatment.
- **Soap Flush:** Mix 2 tablespoons of dish soap in 1 gallon of water and pour over a 1 square foot patch of damaged grass. If 15 or more caterpillars emerge within 10 minutes, treatment is warranted.
- **Bt:** Apply *Bacillus thuringiensis* (Bt) or entomopathogenic nematodes (e.g., *Steinernema carpocapsae*), followed by watering to wash the control agent down to the thatch layer.
- **Insecticides:** Apply registered granular or liquid insecticides, ideally late in the day when the larvae are emerging to feed.
Conservation and Research
Turf Webworms are managed as high-priority turfgrass pests. Research focuses on developing improved turfgrass cultivars with inherent resistance and optimizing the timing and application of biological controls.