The Horse Chestnut Leafminer (Cameraria ohridella) is an invasive pest that has appeared and spread over large parts of the UK in recent years. This Leafminer is a tiny moth that primarily targets Horse Chestnut trees. There can be 3-4 generations of this moth a year from April to October, but the main season in which damage is sustained is from June to September.
The Horse Chestnut Leafminer creates mines in the leaves of the trees, and the moth larvae will pupate in these mines. These mines reach very high numbers, making the leaves of the trees appear white before they turn brown, as pictured above. This gives the tree a prematurely autumnal appearance. The tree is weakened by in the infestation and will produce smaller conkers, but the pest does not appear to kill the trees. It does, however, make the trees more prone to diseases and infections.
There are currently few control methods available to control the Horse Chestnut Leafminer. The best practice to reduce Horse Chestnut Leafminer numbers is to remove the fallen leaves in the autumn and destroy them. This kills a large number of the Leafminer pupae in the leaves. This practice can be combined with the placement of our Horse Chestnut Leafminer Pheromone Traps in the trees from May to September. These traps will attract and catch huge numbers of Horse Chestnut Leafminer moths reducing their ability to breed and lay eggs.