Plantwatch: Autumn and leaves are falling, but for the wrong reasons

A big tree can be infested with about 2m of these tiny leaf miners, just one of several new pests attacking British woodlands

The autumn tree colours are appearing, but all is not quite what it seems. Horse chestnut leaves started falling weeks ago like crispy brown pieces of paper, a sign of leaf miners infesting the trees.

These are the caterpillars of a tiny moth, and a big tree can be infested with about 2m of these pests, which weakens the tree. Even more pernicious is a disease of horse chestnuts called bleeding canker, which can kill the tree.