Cedar Apple Rust on Apple Trees
Cedar apple rust is a fungal infection caused by the species Gymnosporangium juniper-virginianae. It is often confused with other rust infections but is completely different. What makes cedar apple rust really unique is its life cycle. The fungus requires two completely different host plants to complete a cycle. It infects apples and crabapples in the spring and then juniper plants in the late summer. The fungus is much more damaging to its apple hosts than its juniper hosts.
How Does Cedar Apple Rust Affect Apples?
The infection can be severe and can ruin your apple crop if not controlled. Even more moderate infections can be damaging. The damage to leaves will cause them to drop early, especially in dry conditions. After a few seasons, the trees become weak and the apple crop will drop off. The infection also reduces the production of fruit buds on a tree.
Managing Cedar Apple Rust in Apples
Apples with cedar apple rust need special care to overcome the disease and still produce fruit. First, check to see if you have juniper species near your apple trees. If they are infected, they will produce galls in the spring and summer that can grow quite large. They produce distinctive orange tendrils that are hard to miss. Spores from these can infect any nearby apple trees. One way to manage the disease is to remove or destroy any nearby junipers. Or you can just monitor them for galls and either destroy the plant or prune off and destroy the branches with galls. Another way to control for cedar apple rust is to grow varieties of apple that are resistant to the infection: Red Delicious, McIntosh, Winesap, Empire, and others. A fungicide spray can also be used. Your local nursery can help you find the appropriate spray. However, prevention is usually a better way to control this disease in apple trees. About 1,000 feet (305 m.) between apples and juniper species is enough to protect your trees. Also, keep in mind that a low level of infection will not affect your crop very much.
