Question
I have a 12 ft. Ornamental Crabbapple tree that has been growing well for 6 years and now it is developing dead leaves, followed by the whole branch dieing off.  It is happening randomly over the body of the tree, not just in one area.  The leaves are quite full and colorful on this tree. I've trimmed off these dead areas, and within a couple of weeks, another area develops.  And, no, its not fall here...

Answer
Hi. It sounds like it could be apple scab, which is a plant disease caused by the fungus Venturia inaequalis. It also could be a rust fungus known as cedar-apple rust. Both cause early defoliation. The rust fungus is more isolated, while the scab fungus is more universal in spread, so I believe this is what you are seeing. Clean up all the leaves and fruit this fall. Next spring, spray the trees with lime-sulfur while the trees are still dormant and again after leafing. Use a fungicide known as Captan. Repeat again in 10 to 14 days.
Hope this helps