Residents urged to keep their eyes open for moth

Published: 15 May 2019

As the weather hots up, more and more Hertfordshire residents are taking the opportunity to get outside and enjoy the county’s beautiful countryside.


May is National Walking Month and a great time to explore Hertfordshire’s many open spaces and woodlands – particularly in places like Broxbourne Woods National Nature Reserve where oaks are a prominent feature. 


Oak trees are important for wildlife as they provide food and habitat for over 400 species of birds, insects and mammals.  But they are also home to the pest, the oak processionary moth.


These moths are currently predominantly found in the London area, so people are unlikely to encounter their caterpillars in Hertfordshire.  However, if the caterpillars are sighted, take care not to touch them or their nests, and if a sighting is reported in the area pets should be kept under close control.


Oak processionary moth is a pest which established in London following an accidental UK introduction. The caterpillars are covered in tiny hairs which can cause unpleasant reactions in people and pets. These include skin conditions, irritation to eyes and throat, and, in severe cases, breathing difficulties and allergic reactions. The Forestry Commission’s advice is: “Spot it, avoid it, report it.”


Simon Aries, Assistant Director for Transport, Waste and Environment at Hertfordshire County Council, said: “As summer approaches it’s great to spend more time outside enjoying Hertfordshire’s countryside and wildlife.


“Although oak processionary moths are still rare in Hertfordshire, and the adult moths are harmless, the hairs of their caterpillars do contain a strong irritant that can cause unpleasant reactions.


“So if you spot one, please follow the Forestry Commission’s advice and ensure a safe and healthy summer.”


People can use the Forestry Commission’s online reporting system “Tree Alert” ( to identify and report oak processionary moth in its caterpillar stage.  The moths emerge in late spring and despite their similar appearance to several other species, they are easily recognised by a distinctive habit of crawling in large groups, nose-to-tail forming long lines on or around oak trees.


Hertfordshire County Council is working closely with partners to prevent the spread of oak processionary moth and other pests and diseases through our Tree Health Network. For more information visit: