Outbreak of Oak Processionary Moth

Oak Processionary Moth or OPM has been discovered in Hampshire, Warwickshire and Gloucestershire. The Plant Health Service have announced an urgent review of import controls on large oak trees, but is it too little too late?

I last wrote about OPM in July 2012, and warned then:

“Ignoring OPM is not an option – its spread is a disaster already happening – soon impacting our gardens, parks and forests across England unless action is taken urgently. “

Gabriel Hemery, July 2012 Article
OPM oak tree under treatment attracts public interest
OPM oak tree under treatment attracts public interest. Photo Gabriel Hemery

OPM is already an established pest in areas of London, while the rest of the country is designated as a Protected Zone. Swift action is being taken by the Plant Health Service to eradicate recent findings of OPM in Hampshire, Warwickshire and Gloucestershire, including surveillance, tracing work and destruction of both the caterpillars and infested trees. The Plant Health Service has announced an urgent review of import controls on large oak trees (girth more than 8cm at 1.2m above the root collar).

Take Action

If you suspect OPM, you should not attempt to destroy or move infected material yourself as the nests and caterpillars can pose some risks to human health. For more on how to identify OPM, visit https://www.forestresearch.gov.uk/opm

About Oak Processionary Moth

OPM caterpillars feed on oak leaves and can increase trees’ vulnerability to attack by other pests and diseases, making them less able to withstand adverse weather conditions such as drought and floods. These new cases highlight the need for continued vigilance from industry and government to protect the UK’s trees, coming soon after research which indicated that ash dieback may cost Britain many times more than the foot and mouth disease (read more).

The caterpillars can cause serious damage to trees by defoliating entire canopies but this is a minor problem in comparison to their effect on human health. The caterpillars of the third to sixth instars have poisonous hairs or setae that carry a toxin that can cause serious irritation to the skin, eyes, nose and throat of humans and other animals.  If inhaled they can cause respiratory distress, asthma and even anaphylactic shock.

More information


Read more of my posts about Oak Processionary Moth

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