Gymnosporidium rust

Asked May 22, 2019, 1:28 PM EDT

I have a service berry with gymnospridium rust. It's a young bush that is 3 to 4 feet high. How do I treat this fungus? Should I worry that it will spread to other plants?

Columbia County Oregon

1 Response

Thank you for your question. Here is the page in the PNW Handbook which describes the fungus, has a photo of a plant with it, and has control mechanisms: https://pnwhandbooks.org/plantdisease/host-disease/serviceberry-amelanchier-spp-rust

Although this fungus can infect other members of the rose family, the fungus needs a host plant of a juniper or cedar, of which you undoubtedly have some on your property. Only one fungicide, Spectracide Immunox, is approved for homeowner use (H), and fungicides have not been shown to be very effective.

One recommendation is to "Remove or widely separate from all junipers or cedars. Specific junipers or cedars can be removed only when the rust species has been correctly identified. In order to do so, you would need to have a laboratory diagnosis of the species. If you decide you would want that test, this OSU Extension article gives a list of analytical labs in or near Oregon: https://catalog.extension.oregonstate.edu/em8677

Hope this is helpful. Good luck!