What is cedar-apple rust, and how do I identify and manage the disease?

Cedar-apple rust is a fungus disease of apple and cedar and spends parts of its life cycle on each host. It is caused by Gymnosporangium juniperi-virginianae. The fungus can infect leaves and fruit of most cultivars in the eastern region. A notable exception is ‘Delicious’, which is nearly immune. For more information, see this article on Cedar-Apple Rust.

Answer provided by Alan R. Biggs, West Virginia University.