Allotments 4 All

I have 8 mature sycamore trees in my garden(great for leaf mould)  However the problem at the moment is that they are all covered in greenfly.  Never noticed it before.  The underside of the leaves are covered in the beasts and anything that is left underneath the trees ie cars etc are covered in drops of a sticky residue.  Does anyone have any ideas how I can get rid of them .

Yeah, chop the trees down. But seriously, on trees that size there is no way you can de-pest them, you will have to wait for a ladybird invasion.

I can see it now.....swarms of ladybirds flying over Caenarfon Castle!  :o ;D

I didn't imagine big trees to suffer from aphids...don't know why....dumb blonde I guess.  :-\