The Forestry Commission has issued a warning across England as oak processionary moth caterpillars begin hatching, marking the onset of their most dangerous season. From late May onwards, these pests not only defoliate oak trees but also pose significant health hazards to people.
Public health officials advise everyone to avoid direct contact with the caterpillars or their nests. The tiny white hairs covering the larvae and the nests can cause severe skin rashes, eye irritation, and throat discomfort. Handling or attempting to remove nests without professional help is strongly discouraged.
If you encounter these caterpillars, especially in South East England where sightings are common, maintain a safe distance and report the location promptly through the TreeAlert portal.
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Dr Edward Straw, Programme Manager for the Forestry Commission’s Oak Processionary Moth initiative, stressed the urgency of vigilance: “Homeowners are already reporting painful rashes from contact with these caterpillars. Awareness and caution are vital to safeguard health and tree wellbeing during this peak season.”
UK Chief Plant Health Officer Professor Nicola Spence also emphasized the public’s role: “Residents in London, nearby areas, and Derbyshire should avoid any interaction with the moth or its nests. The oak tree is a cherished component of Britain’s natural heritage, and reporting sightings helps control the pest’s spread and protect tree health.”
Named for their distinctive behavior of moving in head-to-tail lines up oak trunks—sometimes forming arrow-like patterns—oak processionary moth caterpillars feed voraciously on leaves. This defoliation weakens trees, leaving them susceptible to drought, disease, and other stresses.
Originating from continental Europe, the moth was first identified in London in 2006, inadvertently introduced via imported trees. Since then, it has steadily spread throughout England, recently reaching new areas as of July last year. The warmer temperatures this spring have accelerated their development, heightening the risk to both trees and humans.
Vigilant public cooperation remains crucial to managing and mitigating the impact of this invasive pest.