Question
I live in Maryland and I have an apple tree that looks very sick.  There are lots of yellow brown spots on all of the leaves (except for the new growth).  On the underside of the leaves, you can easily see little lumpy groups of powdery brown...something.  I think it may be some form of rust, but I'm not sure.  The apples have spots too and they are rotting and falling off.  The spots on the apples look brownish, almost as if it were some kind of bruising-but they're definitely rotten.  We just bought this house, so I know nothing about this tree except that the previous owner obviously didn't take care of it.  What's wrong with my apple tree?  What can I do now and in the spring to get healthy fruit for next year?

Answer
Sounds like cedar apple rust. This disease takes two hosts to complete a life cycle--apple and cedar. The fungus produces spores on the cedar and these go to the apple leaves and fruit and produce spores these spores then go back to the cedar. One of the ways to cut down on these spores is to eliminate the cedars near by or the fungi growths on the cedars--this may not be possible and if not there are several fungicides that can be sprayed on the new apple leaves in the spring that will protect the leaves. The youg apple fruit will also need to be sprayed. Here is a web link that will give more information on cedar apple rust and its control. The second link is to a chart that lists the fungicide and when to spray.

http://ohioline.osu.edu/hyg-fact/3000/3024.html

http://ohioline.osu.edu/b780/pdf/Table11.pdf