Oak Processionary Moth

Oak Processionary Moth (OPM) identified within the London Borough of Bexley

Oak Processionary Moth caterpillar

What is Oak Processionary Moth (OPM)?

Oak Processionary Moth is a non-native insect originating from Southern Europe and has been in the UK since 2005.

How will it affect me?

The caterpillars of this moth primarily live and feed on Oak leaves, but they can also be found on the ground around an infected tree. The caterpillars are easily identifiable as they move together as a group in a column, head to tail in a procession - hence their name Oak ‘Processionary’ Moth.

rash from Oak Processionary Moth caterpillar

Although the adult moths are harmless, the hairs of their caterpillars contain a strong irritant. Contact with these hairs can cause severe irritation with skin rashes, less commonly: sore throats; breathing difficulties; and eye problems.

Both people and animals can be affected by touching the caterpillars, their nests, or if windblown hairs make contact with the skin. The greatest risk period is May to July, but the hairs from the caterpillar can be present on old nests and could be blown or touched at any time of year.

How it affects the trees

The caterpillars’ preference for a diet of oak leaves means a large infestation can strip a tree bare, which reduces its ability to capture sunlight and make food. A healthy Oak can regrow its leaves in a few weeks. However, over time, these attacks may reduce an Oak’s tolerance to stresses such as drought, floods and other pests and diseases.

For further information, please visit Forest Research.