‘What is wrong with the Horse Chestnuts these days?’ This question is often asked because these popular trees looked especially sickly in 2008. They are not the only species suffering from pests and diseases but the Horse Chestnut is perhaps the most prominent English patient, the disfigured browning leaves being particularly obvious this year.
The culprit, a tiny moth amusingly named the Leaf Miner, causes the problem through its larvae getting inside the leaf layers and munching away the spongy chlorophyll inside. Some claim that it was first identified in Wimbledon and spread remarkably quickly heading northward in the UK, having originated in Germany or Holland. The good news is that it is not fatal. By mid to late August the leaves have done their job so the browning may not be too harmful. But the not so good news is that the attack seems to have been getting earlier in the year which could gradually weaken trees. The remedies? Burn all the fallen leaves in the tree’s vicinity to reduce next year’s attack or, more realistically, wait for a really cold winter to do the job.
The paltry numbers of conkers in 2008 was not caused by disease but poor pollination this year. Poor old squirrels.
More serious for these trees is ‘bleeding canker’, visible by lesions on the trunk with a rusty brown staining. This bacterium has become increasingly common since 2000 and can be fatal. But some trees, including older trees, do recover. At least one large Horse Chestnut in Coates appears to have succumbed in the last year or so, and one tree in a local Ciren Tesco car park died in just six months. A treatment may be on the horizon but has yet to be licensed for use.
Geoff Moore, Voluntary Tree Warden (with thanks to Guy Watson for his expert guidance)
