Pestipedia

Tussock Moths

**Tussock Moths** (Family Erebidae, Subfamily Lymantriinae, e.g., White-marked Tussock Moth—*Orgyia leucostigma*) are common pests of forest and urban trees, including deciduous and coniferous species. The conflict is **defoliation and human nuisance/health risk**: the larvae (caterpillars) feed on tree leaves, causing significant **defoliation**, and they possess **urticating hairs** (stinging hairs) that can cause severe **allergic reactions, dermatitis, and respiratory irritation** in humans upon contact.

Taxonomy and Classification

Tussock Moths belong to the order Lepidoptera (Moths and Butterflies). They undergo complete metamorphosis. The caterpillars are highly distinctive due to their tufts (tussocks) of hair.

Physical Description

Adult Larvae are medium-sized, 1 to 1.5 inches long.

  • **Larva (Key ID):** Hairy caterpillars with distinct, dense **tufts of hair** (tussocks) running along the back (often four white/yellow tufts) and two long, black hair pencils protruding from the front and one from the back. Color is often gray/black with red spots.
  • **Adult Moth:** Males are winged and active. Females of many pest species (e.g., White-marked Tussock Moth) are **wingless** and remain on the outside of their cocoon to lay eggs.
  • **Damage Sign (Key ID):**
    • **Defoliation:** Stripped branches, usually starting at the top of the tree.
    • **Cocoons:** Prominent, often whitish cocoons on the bark or branches.
  • **Conflict:** Defoliation and severe skin/respiratory irritation.

Distribution and Habitat

Tussock Moths are found globally. Their habitat is the foliage and branches of their wide range of host trees.

Behavior and Conflict

The conflict is the health risk associated with the urticating hairs.

  • **Health Hazard:** The detached hairs can be carried on the wind or equipment and penetrate human skin and mucous membranes, causing painful, persistent rashes.
  • **Flightless Female:** The wingless female lays eggs on the outside of her cocoon, leading to a highly concentrated infestation in the immediate area.

Management and Prevention

Control is integrated pest management (IPM), focusing on physical removal and biological control.

  • **Physical Removal (Key):**
    • **Egg Masses/Cocoons:** During the dormant season, scrape off and destroy the egg masses (often covered with white or brown hair) and cocoons on the tree bark. **Wear gloves and protective clothing** when handling infested material.
  • **Biological/Chemical Control:**
    • **Bt:** Apply *Bacillus thuringiensis* (Bt) to the foliage when the larvae are small.
    • **Insecticides:** Use registered insecticides only when populations are high and defoliation is severe, ensuring the application is timed for the early larval stages.

    • Conservation and Research

    Tussock Moths are managed as forest and urban pests, primarily due to their health risk. Research focuses on their population dynamics, the chemical properties of the urticating hairs, and the use of parasitic wasps and flies as natural enemies.