A caterpillar which can harm humans, animals and plants has been spotted in Cambridgeshire and Hertfordshire. The sightings follow similar outbreaks in Germany and the Netherlands.
The larvae of the Oak Processionary Moth have tiny hairs which can trigger allergic reactions and skin irritation. They also weaken oak trees.
Trees and Woodlands Officers from Dacorum Borough Council are putting up safety notices on any affected public trees in the borough. Additionally, the council are asking local residents to be vigilant, especially with young children who may be exploring trees this summer.
The caterpillars and nests are only likely to be found on oak trees.
"We are working with the Forestry Commission to control the spread of this harmful species. If you discover an OPM nest or caterpillar, we ask that you 'spot it, avoid it, report it'."
Affected counties in England include Cambridgeshire, County Durham, Devon, Dorset, Essex, Gloucestershire, Greater Manchester, Hampshire, Hertfordshire, Kent, Lancashire, Leicestershire, Lincolnshire, London, Merseyside, Middlesex, Nottinghamshire, Oxfordshire, Southampton, Staffordshire, Suffolk, Surrey, Warwickshire, West Midlands, Wiltshire and Yorkshire.