Oak Processionary Moth was first identified in London
in 2006 and has since spread to some surrounding
counties. The caterpillars and their nests contain
hairs which can cause itchy rashes, eye and throat
irritations, and should not be touched under any
circumstances at any time. The greatest risk period is
May to July when the caterpillars emerge and feed
before pupating into adult moths.
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. A
government programme is in place to limit their spread
from areas where they are present.
The pest is established in London and surrounding areas
but the majority of the country is designated a
Protected Zone, which means it is free from the pest.
The Forestry Commission, working in partnership with
others, have an annual programme in place to tackle the
pest, with an ongoing programme of surveillance,
treatment and research.
Andrew Hall, Forestry Commission Operations Manager,
said:
At this time of year, many people are enjoying green
spaces and it’s really important for the public to be
aware of the risk of tree pests like Oak
Processionary Moth and to report any sightings via
our TreeAlert website
or by calling the Forestry Commission. This will help
us with our programme of treatment and enables us to
slow the spread of this pest.
Any sightings should be reported to the Forestry
Commission via its Tree Alert
online portal. Alternatively, people can
email opm@forestrycommission.gov.uk or
call 0300 067 4442.
Since 2012, the government has invested more than £37
million in tree health research; this includes a
dedicated programme of research on oaks and the pests
that threaten them, such as Oak Processionary Moth.
The Government has also introduced tighter biosecurity
checks at the border, and in 2019 introduced further
restrictions on the import of oak trees to England
following a number of interceptions of the pest.
How to identify OPM caterpillars
Nests are typically dome or teardrop-shaped, averaging
the size of a tennis ball. They are white when fresh,
but soon become discoloured and brown. The caterpillars
have black heads and bodies covered in long white hairs
which contain proteins which can cause itchy rashes,
eye, and throat irritations. They can also occasionally
cause breathing difficulties in people and pets, so
should not be touched under any circumstances.
For more information on how to identify OPM, including
common mistaken species, visit www.forestresearch.gov.uk/opm.
