What is oak processionary moth?
Oak processionary moth originated in southern Europe and has been a recognised pest since 1995. It was accidentally introduced to the UK in around 2005 via the import of an infected oak tree. Over time the problem has spread north, affecting France, Germany, Belgium and Holland.
As the name suggests, oak processionary moth mainly affects oak trees; however, this pest has been found on other broad-leaved trees like beech and birch trees.
In order to minimise the impact and spread of oak processionary moth in the UK, it is subject to a government-led survey and control programme.
What areas of the UK are affected by oak processionary moth?
Initially, the outbreak was contained within the M25 radius. However, despite concerted eradication and control attempts, cases of oak processionary moth have been identified further afield across the UK.
As elimination of the pest is no longer a viable goal, efforts are being made to slow down its’ spread and avoid further outbreaks.
How to identify OPM
Oak processionary moth lives almost exclusively in oak trees, although, as mentioned above, they have been spotted in other broad-leaved trees. The caterpillars of the oak processionary moth are a pest that can be hazardous to the health of oak trees, people and animals.
The caterpillar’s tiny hairs are irritating to both humans and animals. When these hairs make contact, they can cause itchy skin rashes, can irritate eyes or throat and, in some cases, may cause breathing difficulties.
The Forestry Commission has created this useful leaflet to help the general public identify oak processionary moth. It explains that “the caterpillars move in nose-to-tail processions, in oak trees or on the ground, hence their name. They often cluster together and eat oak leaves.”
Identifying oak processionary moth damage
The caterpillar of the oak processionary moth can strip whole oak trees bare, thus leaving them vulnerable to other pests and diseases. What’s more, damaged trees are less able to withstand the effects of natural events like floods, storms or drought.
If left to spread unchecked, oak processionary moth could quite conceivably destroy the UK’s precious oak tree population and put wildlife habitats in danger.
For this reason, you should immediately report suspected oak processionary moth damage to the Forestry Commission.
When are they visible?
The oak processionary moth lays its eggs in the summer, with the caterpillars beginning to emerge the following April. According to the Forestry Commission leaflet, the presence of oak processionary moth may be identified by “white, silken webbing trails and nests – usually dome or teardrop-shaped – on oak trunks and branches (not among the leaves)”.
Nests vary in size ranging from just a few centimetres to several feet across in some cases. Multiple nests may be found in a single tree, and they may be located at any height. The nests can remain attached to the tree for many months after the caterpillars have hatched.
What to do if you see oak processionary moth
‘Spot it, avoid it, report it’ is the advice given by Forestry Commission researchers Forest Research.
It’s important to learn to spot the signs of oak processionary moth, avoid touching or going near it and notify sightings to the Forestry Commission via TreeAlert or by email to opm@forestrycommission.gov.uk.
Do not attempt to remove it yourself.
To prevent further spread of oak processionary moth, the caterpillars and nests must be removed by an appropriately trained arborist who has the necessary equipment. They will know how to dispose of the nests properly to avoid the further spread of this dangerous pest.
Advice for tree owners and managers
If you own or manage oak trees in an area with oak processionary moth, you have a duty of care to people and animals. It is your responsibility to monitor and inspect your tree(s) for potential outbreaks of oak processionary moth. Strict government guidelines are in place regarding the movement of oak trees to prevent the spread.
Removal and treatment of OPM
Early identification is the most effective way to deal with OPM. The tree needs treatment with specialist insecticides; you can only do this during April and May. After this time, the nests and caterpillars need to be manually removed.
During the removal of OPM, trained arborists will wear hazmat suits and use specific equipment to remove the nests before disposing of them as hazardous waste.
Call us
If you are concerned that you may have signs of oak processionary moth (OPM) on your property, contact the team on 02382 440473 to arrange an urgent tree inspection.
