Why are horse chestnut trees looking so ill?
Horse chestnut leaf-mining moth (Cameraria ohridella) has been a serious problem over the past few years. The pest disfigures horse chestnut trees from midsummer onwards, often making them look as if autumn has come early. This leaf miner was seen in London in 2002 and has since spread rapidly across Britain. It has reached parts of northern England, but is not yet as far north as Scotland. Small, insignificant-looking moths lay eggs on foliage in summer and the resulting larvae burrow inside the leaves, making tunnels in which they later pupate. Adult moths emerge from the mines and repeat the cycle; several generations can occur in one summer. At the end of the season, pupae wait out the winter inside fallen leaves. Trees are not killed and always come back into leaf in spring. Eradication is impossible; clearing and burning or bagging fallen leaves can reduce the problem. 22 What chemicals can we legally use? This year there have been a number of changes to the pesticides and herbic
