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Oak Processionary Moth

Posted by Agrigem Team on 06 August 2019 in Trees, Plants & Ornamentals
Oak Processionary Moth

Native to southern Europe, the Oak Processionary Moth has been found in various areas of the UK over recent years; the most recent sighting being this year on a collection of imported trees.

What are they?

They are called the Oak Processionary Moth because of the trees they target (oak trees such as the Turkey Oak and the Common Oak) and because of the way they move nose to tail in procession on the tree.

The adult moth will lay eggs between July and September on branches and stems of oak trees. They will then overwinter until March-May time the following year when they will hatch into a caterpillar. Once the caterpillars have hatched, they can remain as larvae for many weeks as they go through 6 growth stages. As they begin to feed and grow, they will start to move down the tree building nests on branches as they go. In the following June and August, the caterpillars will pupate in the nests, and then from July to September the adult moths will emerge.

What damage do they cause?

It is the caterpillars (larvae) of the Oak Processionary Moth which are the most damaging to oak trees. Both of Britain’s most common oaks are susceptible- the Turkey Oak (Quercus Cerris) and the Common Oak (Quercus Robur) but other less common varieties are also affected.

The caterpillars will eat the leaves of the Oak trees very quickly leaving just the skeleton veins of the leaf. However it is not only oak trees at risk! Whilst the caterpillars will complete their life cycle solely on oak trees, they will move onto other plants, such as birch, beech and hornbeam, to feed after they have finished with the oak.

Unfortunately, the caterpillars do not only cause problems for trees, they also pose a threat to humans. As Oak Processionary Moth caterpillars get older they develop thousands of tiny urticating hairs which contain an irritating substance called thaumetopoein. In most people this will cause an itchy rash, but some people can experience sore throats, eye irritation or breathing difficulties. You do not necessarily have to touch a caterpillar to experience symptoms; the hairs can travel when they are blown by the wind.

For any more information about the Oak Processionary Moth or how to control it, please get in touch.

The Agrigem Technical Team