People across the UK are being warned about the Oak Processionary Moth caterpillar, which can cause severe health reactions and send people to hospital. The caterpillar, which carries thousands of microscopic hairs containing an irritant protein, is spreading rapidly across the country.
Garden expert Luke Newnes at Hillarys said the moth was accidentally introduced to the UK in 2005 via imported oak trees from the Netherlands. It is now established across London and surrounding counties, with outbreaks confirmed in Hampshire, Warwickshire and Gloucestershire. The recent record-breaking May heatwave has accelerated hatching, pushing the high-risk caterpillar season earlier than usual and producing larger populations.
Each Oak Processionary Moth caterpillar carries thousands of microscopic hairs containing thaumetopoein, an irritant protein. According to the British Journal of General Practice, contact with these hairs can cause urticating dermatitis within one hour, producing intense itching, skin rashes and eye inflammation. Inhaling the hairs can cause coughing and breathing difficulties. The hairs remain active in shed skins and old nests for years.
The caterpillars are highly visible, moving in distinctive nose-to-tail processions on oak bark and building silken nests the size of a golf ball to a rugby ball on trunks and branches. The Forestry Commission runs annual treatment programmes from mid-April, and professional treatment per tree costs between £200 and £500 or more.
Newnes advised anyone with a mature oak tree in London, the South East, or who has planted an imported oak anywhere in the UK in recent years, to check their trees from the ground now. He warned that the caterpillars' airborne hairs can settle on garden furniture, children's toys, trampolines and paddling pools, and can be carried indoors on clothes and towels dried on a line near infested trees.
