Answer: Bring in a sample of the spore horns (or telial horns) of the Cedar Apple Rust pathogen. This sample was brought in today from a Henderson County homeowner.
The fungus that causes the disease, Gymnosporangium juniperi-virginianae, is unusual because it must spend a phase of its life cycle as a parasite on Juniperus species, such as red cedar or ornamental junipers and a part of its life cycle on apple or crabapple trees.
Cedar-apple rust can be severe on apple, therefore Henderson County apple growers are more aware of this disease than most homeowners. Infections of apple fruit result in lower fruit quality and early fruit drop. Leaf spots may cause early defoliation, especially during dry summers. If trees are defoliated several years in a row, they become weakened and stressed. Fruit bud formation may be reduced after one year. The disease is not as harmful to juniper, causing galls but not severely affecting plant vigor.
Click on the link for more information on Cedar Apple Rust.