· Gardenality.com's Answer
· Hi Irina,
If you have Apple Trees near by it may be Cedar Apple Rust. Cedar Apple Rust, however, does have more of an orange color. The way you've described your problem above does make it sound a lot like Cedar Apple Rust.
During rainy, wet weather in the spring, spore horns develop from galls on infected junipers. Spores are spread via wind and rain to leaves on apple and crabapple trees. Infected leaves will develop obvious yellow-orange-red spots apparent from both the upper and lower leaf surfaces. In late summer, hair-like tendrils develop on the underside of infected leaves. Spores from these tendrils spread to susceptible junipers and infection occurs. The fungus grows within juniper twig tissue for approximately 20 months, forming an enlarging gall on the twig. Cedar-hawthorn rust and cedar-quince rust have similar life cycles to cedar-apple rust.
The rust fungi are dependent upon both the juniper host and the alternate (apple, crabapple, hawthorn, or quince) hosts for survival. Removal of one or the other breaks the life cycle of the fungus, preventing disease. A distance of ¼ mile between junipers and alternative hosts is helpful. In late winter, remove and destroy galls on junipers. Usually, rust does not cause sufficient injury to warrant fungicides. If it is a chronic problem, causing leaf drop and poor tree vigor, registered fungicides may be used on apples, crabapples, hawthorn and quince. This should be done at 7-10 day intervals when juniper galls are producing spore horns. When
spring weather is dry, fungicide applications are generally not required.