Question
We have a couple of trees at the end of the field they are covered in what look like a moth's cocoon or spider's web. The web is almost like a stocking going up the entire trunk and then covering all the leaves of the entire tree which is about 25-30 feet tall. The leaves although still green are somewhat shrivelled and have holes in them.
I am not sure what variety the tree is, It has some small black berries on it now in September, the leaves are beech like and the trunk is smoothish but I do not think it is a beech tree, part of one of the trees has fallen down. I live in Aberdeenshire in Scotland

What do you think has colonised this tree and how do I get rid of it?

Answer
Sounds like the spindle ermine moth. They will spin their web over the tree and eat the leaves. First check and see if there are caterpillars in the web. I would guess they have done their job and left. IF you see caterpillars you can spray the webs with and insecticide --one recommended in the US is Orthene. Another which is slower is Bt. Or you can mechanically remove the webs and the caterpillar in them. Here is a web link to ore information on this insect. It may defoliate the tree but will not kill it. The tree will leaf out again next spring. http://www.butterfly-conservation.org/uploads/BC%20web%20site%20-%20Ermine%20mot(2).pdf