The ends of branches drop leaves and turn black, then drop. What is the name of the beatle - I believe it is a beatle - that causes this and what to do?
magnolia die back
The only problem I'm aware of that affects Magnolias is bacterial leaf spot. The do ocassionally suffer from wind burn, aphids and scale, but I don't know of a beetle that attacks. That's not to say there's not one though. Take a look at this link and see if it looks like your problem. http://www.mobot.org/gardeninghelp/plantfinder/IPM.asp?code=185&group=8&level=c
What you're describing sounds like fire blight, but I don't think it affects Magnolias. If you can't figure it out, maybe send a sample to your county extension agent or take it to a nursery and see if they can help. Sorry I'm not more help.
Crow