are they being defoliated or are the leaves turning brown and crispy? it could be similar to the Horse Chestnut Leaf-miner, Cameraria ohridella that eats away on the inside of the leaf. So far the trees haven't died as they come back into leaf the following year.

can you post a photo of the problem?

have you reported the problem to the council or the woodland trust or Kew?

It’s important we find out, when you say lots of trees dying are these on your land or roundabout where you live, I have not noticed any sycamores dying here in Derbyshire, I look after a small woodland of sycamores and all are doing well, the only problems I have found over the years is some years they get blackspot on the leaves but the trees still do fine, the only other problem that I have noted over the years is black aphids some years never a problem and some years they are covered in them and the honeydew coats the leaves and ground below and this year is a bad year they are covered in them, like I say it is very important that we find out, yes speak to the council but normally they carnt be bothered to follow inquiries up.

The affected trees start losing their bark,in flakes, then die completely. They look like they have been burnt.the council know and their reaction is to cut down the dead trees. The hot spot seems to be Thornes park, although it must be said I don't get about as much nowaday s.

Oh dear. Round here its the ash trees that are slowly dying. We are surrounded by Ash and Sycamore - if they all die the whole landscape will change - and there will be no shelter from the strong SW winds either.