shigo's pruning books are of biblical proportions to the climber, but its all about how they respond as a "self optimizing structure"
there's a german dude called Claus Mattheck forgive me if the spelling is wrong, but he is famous for his whacky VTA or visual tree assesment pictures. these are great to understand the strain trees are upon and where likely weaknesses are. for pest and disease im not sure as its different in the states to here, but anything relating to pathenogenic fungi or saprophytic fungi will help with some stuff. i know in the states there's more common threats from vectors such as spruce beetles and other wood boring insects as well as sap suckers so try to search for a book on the different orders of insects too.
J