Cedar-Apple Rust of Juniper

Disease Information

Cedar-Apple Rust

 Symptoms and damage

This fungal disease of apple, crabapple and Eastern red cedar is caused by several species of Gymnosporangium. The disease not only affects Juniperus species including Eastern red cedar (Juniperusvirginiana) but requires another host plant, apple or crabapple, to complete its life cycle. This disease spreads from junipers to the apple and then back to juniper. It can be a severe problem wherever these two are grown together. Eastern red cedar is the most commonly infected juniper. On juniper, hard, brown, up to 2-inch diameter galls form near the ends of the branches in the summer. In the spring following a rain, the galls produce large, orange, gelatin-like tendrils, full of spores, which can blow a half-mile to infect nearby apple and crabapple trees.

Symptoms that occur on the apple trees appear as yellow spots on the upper leaf surface. In the late summer, these yellow spots form spores that are spread to the leaves and twigs of nearby junipers (within 2 miles) to infect them.

Management

Select resistant varieties of apple (such as `Enterprise`, `Pristine`, `Liberty` or `Redfree`) or juniper. Prune out all galls on the juniper, if possible. Do not plant apple, crabapple and Eastern red cedar trees in the same area. If disease is severe enough to warrant control, or a particular specimen plant is affected, select a fungicide containing mancozeb or propiconazole.

 



Share this article