I'm not absolutely sure about this, but there is an insect that is associated with these evergreens. I first heard of it by an article from Alan Titchmarsh. I don't think there is anything you can do to save them either. sorry it isn't better news.

So far as I know there is nothing you can do... send Bamboo a pm as she knows about this problem.

thanks to rose 1949 and moon growe for your reply. my whole garden is surrounded by this hedge I cant think what is going to happen if it continues to spread, I need to find out what the insect is and see if I can stop it.

Take a look at the RHS info. copy and paste the link into your web browser

http://apps.rhs.org.uk/advicesearch/profile.aspx?pid=132