What disease is currently affecting horse chestnut trees in the uk?
The affliction which turns the leaves brown prematurely is a tiny leaf-mining moth which lays its eggs on the leaves. The grubs hatch and bore their way into the structure of the leaf, causing it to turn brown. The infestation is not hazardous to the tree, just unsightly. More serious is a fungus which is attacking some horse chestnuts. This is characterised by a lesion on the bark, usually on the trunk, through which the fungus first gains hold and then spreads. The lesion make the wood of the tree visible through the bark, and is usually surrounded by a black sticky substance. This is dangerous to the tree, which may have to be felled. Some trials are currently underway in Holland using garlic in solution, which appears to be so far helping both conditions.
