Rusty tussock moth

Orgyia antiqua

1. Identification

• Common name: Rusty tussock moth; Vapourer moth
• Scientific name: Orgyia antiqua L.
• Order: Lepidoptera
• Family: Erebidae (formerly Lymantriidae)

2. Pest description

• Very distinctive caterpillars, with dorsal tufts of yellow hairs (“brushes”), dark lateral tufts and a red terminal tuft; reaching 30–35 mm.
• Dimorphic adults: winged males, orange‑brown, with feathery antennae and a wingspan of 25–30 mm; wingless females, with a bulky, whitish body, remaining near the cocoon where they emerge.
• Defoliating species, with very voracious caterpillars.
• May occur in forest environments, gardens and urban areas.

3. Main hosts

• Rosaceae: apple tree, pear tree, plum tree, cherry tree.
• Oak, willow, birch, hazel.
• Ornamental shrubs and various spontaneous broadleaf species.
• Highly polyphagous species, capable of attacking more than 100 plant species.

4. Symptoms and damage

• Partial or total defoliation, especially in young trees or ornamental shrubs.
• Leaves notched or completely consumed, leaving only the veins.
• Decline in plant vigour in intense attacks.
• In urban environments, it may cause public health problems due to the urticating hairs of the caterpillars.

5. Biological cycle

• Eggs laid in masses on the female's cocoon, where they remain during winter.
• Caterpillars emerge in spring and feed for several weeks.
• Pupation in silky cocoons fixed to the vegetation.
• Adults emerge in summer; generally one generation per year.

6. Monitoring

• Direct observation of caterpillars and their characteristic tufts.
• Searching for egg masses on old cocoons.
• Assessment of the intensity of defoliation in trees and shrubs.
• Reinforced monitoring in parks, gardens and urban areas.

7. Management measures

• Cultural: manual removal of cocoons and egg masses; destruction of heavily attacked branches.
• Preventive: regular inspection of ornamental and fruit trees; management of spontaneous vegetation.
• Biological: promotion of natural enemies (parasitoids and predators).
• Integrated protection: judicious application of Bacillus thuringiensis in the early stages of the caterpillars; use of authorised insecticides when necessary and in accordance with intervention thresholds.

Bibliographic references

• CABI – Invasive Species Compendium – Orgyia antiqua.
• EPPO Global Database – Orgyia antiqua.
• Alford, D. V. (2007). Pest and Disease Management Handbook. Blackwell Publishing.
• Carter, D. J. (1984). Pest Lepidoptera of Europe. Dr W. Junk Publishers.
• Wagner, D. L. (2005). Caterpillars of Eastern North America. Princeton University Press.