Oak Processionary Moth

Thaumetopoea processionea

Overview

  • Photo credit: S. Hamilton, DAERA Plant Health Inspection; Max Blake; Henry Kuppen

  • Oak processionary moth –Thaumetopoea processionea

  • Description:
    • The oak processionary moth (OPM) is a greyish-brown non-descript moth (wingspan is 25-35mm). The caterpillars are covered in stiff hair, and are seen most active in late spring to early summer where they move in large groups in nose-to-tail processions. They are covered in long white hair, which hides shorter irritating hair, and have a grey body with a dark head. The caterpillars are almost exclusively found on oak trees, but if in short supply they may be seen on sweet chestnut, hazel, beech, birch and hornbeam; they may not be able to pupate if they remain on other tree species.

  • Origin and Worldwide Distribution:
    • The OPM is a native of central and southern Europe. It has been introduced to Great Britain, the Netherlands, northern Germany and Sweden through the trade of live oak trees. In Great Britain, it was discovered in West London in 2006 and has expanded due to natural population growth and similar introductions. It may colonise other parts of England and Wales if it is allowed to spread.

  • Potential or Known Impacts:
    • The OPM is a tree pest as its caterpillars feed on the leaves of several oak species. If densities are high enough, the caterpillars can strip oak trees bare, which leaves them vulnerable to pests, diseases, and environmental stressors, like drought. The picture below shows an oak tree that has been severely damaged by OPM caterpillars.
    • The caterpillars’ stiff hair poses a threat to humans and animals as these hairs come loose and can be carried on the wind or collect under trees. When these hairs come into contact with skin or mucous membranes (eyes, nose and throat), an irritating protein is released into the person or animal. Skin and eye irritations, sore throats, breathing difficulty and rarely allergic reactions may occur.

  • How could it get here?
    • It could get here through imports of live oak trees or natural spread from an area of introduction.

  • Is it present in Ireland or Northern Ireland?
    • It has recently been recorded in Dublin, Ireland in July 2020. The caterpillar nest was destroyed, but the risk remains of further introductions. It is not present in Northern Ireland.  

  • Methods for Prevention:
    • Report all sightings through Treecheck or CEDaR.
    • Don’t import oak trees from infested areas.

Species Related Files:

Invasive Species Ireland

Invasive Species Ireland