Goat Moth

Cossus cossus

1. Identification

• Common name: Goat moth, red wood borer
• Scientific name: Cossus cossus L.
• Order: Lepidoptera
• Family: Cossidae

2. Pest description

• Adults: Large moths (≈ 65–100 mm wingspan); greyish wings with irregular patterns; robust body.
• Larvae: Large caterpillars (up to 80–100 mm), reddish-brown, with a dark head; emit a strong characteristic odour; develop inside the trunk and thick branches.
• Eggs: Laid in cracks in the bark or near wounds on the tree.

3. Main hosts

• Various broadleaf species: poplar, willow, oak, apple, pear, walnut.
• Other susceptible ornamental and forest trees.

4. Symptoms and damage

• Holes in the trunk and branches, with the expulsion of sawdust mixed with exudates.
• Deep galleries in the wood, compromising the structure of the tree.
• Cracks and necrotic areas in the bark.
• Progressive decline, dry branches and possible death of the tree in severe attacks.
• Strong, characteristic odour associated with the larvae.

5. Biological cycle

• Winter spent as a larva inside the galleries.
• Prolonged larval development (2 to 3 years).
• Pupation inside the trunk or close to the bark surface.
• Adults emerge in summer.
• Females lay eggs in cracks in the bark or wounds.

6. Monitoring

• Observation of sawdust and exudates at the holes.
• Identification of active galleries through recent openings.
• Search for dry branches and signs of decline.
• Assessment of weakened or wounded trees, more susceptible to colonisation.

7. Management measures

• Cultural: Removal and destruction of heavily infested branches; improvement of tree vitality; avoid wounds in the bark.
• Biological: Conservation of local natural enemies (parasitoids and predators of larvae).
• Integrated protection: Regular monitoring; early intervention in trees with initial signs; chemical treatments with limited efficacy owing to the cryptic habit of the pest.

Bibliographic references

• EPPO Global Database – Cossus cossus.
• CABI Invasive Species Compendium – Cossus cossus.
• Alford, D. V. (2007). Pest and Disease Management Handbook.
• Speight, M. (2013). Wood-boring Lepidoptera in European forests.