My Discovery apple tree is about 10 years old and has produced a good crop of apples each year, but it appears to be dying. Two years ago all the leaves on one of its branches withered and died prematurely and the apples on that branch stayed small in size. Last year the condition spread to nearby branches and this year it is affecting even more, so that half the tree is affected.
I have just cut off the first affected branch to inspect it but the cut edge looks OK. The condition only becomes apparent in the summer. The springtime development of the affected branches seems to be normal but during July the leaves wither and die, the apples stop swelling and fall off prematurely. None of my other apple trees are affected at all. I live in the Eden Valley in Cumbria.