Sorry - the second link on wivvles post gives details of fungicidal and insecticidal teas which I though may be useful as a last resort. Trouble is I do not want to kill worms, ladybirds, ground beetles, hoverflies, bumble bees etc. Just thought that if knew anything about that side of things it would be very useful.
PS - how high above soil level should the lip of my beer traps be to stop innocents such as ground beetles wandering in?