Apples trees in the US are dying at alarming rates. Rapid apple decline, or RAD, begins on a single limb. The leaves will curl up, turn yellowish-red and eventually spread to the other limbs until the entire tree is dead. This disease can also spread from one tree to another tree. Scientists are uncertain on the cause of the epidemic. 

For more info see: https://www.mnn.com/earth-matters/wilderness-resources/stories/apple-trees-are-mysteriously-dying-all-across-america-and-nobody-knows-why