Illustrated identification guide — PestControlBasics.com
🔍 Identification
Caterpillars: 35-45mm; dark with orange-red side stripes; move in long single-file processions (the diagnostic behavior — like a living train). Nest: white silken tent high in pine trees, visible in winter. Urticating hairs: microscopic barbed hairs covering caterpillars cause severe dermatitis, eye damage (ophthalmia), throat swelling, and potentially fatal reactions in dogs. Do NOT touch or approach.
🧬 Biology & Behavior
Currently established in southern Europe, North Africa, and the Middle East — expanding northward with climate change. Risk to US: interception at ports on nursery stock and ornamental trees. Not established in the continental US as of 2026. If you see processions of caterpillars in a line or white silk tents in pine/cedar trees in the US: photograph from a distance and report to USDA APHIS and your state department of agriculture immediately.
⚠️ Damage & Health Risk
Pine defoliation and tree death; severe urticating hair reactions in humans and animals — dogs are particularly vulnerable (throat swelling can be fatal); significant public health and veterinary emergency risk in affected areas.
🔧 DIY Treatment
In established areas (Europe): pheromone traps for male adults; tree barrier bands preventing processions from reaching soil for pupation; Bt kurstaki spray in early larval stage when hairs are less developed; biological control (parasitoid wasps). In the US: report suspected sightings — do not attempt DIY control of a potential new invasive.
👷 When to Call a Pro
USDA APHIS coordinates response to new invasive detections — contact them if suspected. Professional assessment required for any European nursery stock with silk tent structures.