When looking at the lovely photos Lorna took of the Whitworth Park bioblitz, I spotted that she’d caught something rather interesting in her pictures of horse chestnut leaves. When pictured against the light you can clearly see dark blobs surrounded by paler leaf tissue.
This damage is caused by the horse chestnut leaf miner (Cameraria ohridella). The larvae of this moth live between the upper and lower surface of the leaf eating to create a mine which appears as the paler leaf tissue. These larvae then pupate inside the leaf before emerging as tiny moths. In these photos of the leaves in Whitworth Park, the pupae are at the centre of the darkest spot in the mine.
After spotting these mines, I went back to the park to collect some leaves to show at the Museum’s ‘Nature Discovery’ Big Saturday and found huge swarms of these little moths all over the lower branches of the tree. Hopefully we will manage to collect some to add to the Museum’s entomology collection to match the damaged leaves that I’m preparing to add into the herbarium collection.
This moth was originally discovered in Macedonia, and has worked it’s way across Europe (probably with help from people and their cars). It arrived in the UK in 2002 when it was first spotted causing damage to trees on Wimbedon Common. Ten years later and the moth seems to be thriving in Manchester too. I’m going to add our sighting of the infested tree in Whitworth Park to the data for the Conker Tree Science – Alien Moth Survey Mission. If you have a horse chestnut tree growing near you, you can add your tree to the survey too – whether or not the moths have managed to find it.