Silver Birch Tree

Short of spraying (which personally I hate to do as it causes more problems than it cures), one of the common problems is that natural predators can't deal with the aphids as they are often 'guarded' by ants. Are there lots of ants climbing up and down the tree? If there are, putting some sort of sticky grease band on the trunk should deter the ants and allow the aphids to be attacked by ladybird larvae or hover flies.

Bertiefox

Thanks for this I shall look at the tree this afternoon and see if there are indeed ants on it.