amenlanchier gymnosporagium

Asked October 24, 2018, 10:01 AM EDT

What spray can I use in Carroll Co. to prevent rust returning next year? I hand picked the infected fruit from the tree and pruned the infected branches this year after I discovered the infection. I didn't realize when I planted two juniper shrubs near the tree that they were a host for the spores. Also, can the shrub hosts be treated as well? I'd rather not remove the shrubs, but if that is the only solution, I'll do it. Thanks for your help. Taneytown

Carroll County Maryland serviceberry rust trees

1 Response

The rust disease does not kill the tree but it looks disfiguring. This can be common in cool wet weather. We received a lot of reports this year as our weather has been favorable for it. We do not recommend trying to control rusts on ornamentals with fungicides. In the landscape, damage to either host is not severe enough to warrant fungicide applications.

Serviceberry is in the rose family, so it is susceptible to many of the same disease and insect pest problems that are seen in other species within the family (e.g. apples and pears). The alternate hosts of this disease are Eastern red cedars (Juniperus virginiana), Common juniper (J. communis), and Creeping juniper (J. horizontalis). The fungus carries out its lifecycle between the two host plants. The best recommendation is to select disease resistant varieties. No chemical control is recommended for ornamental plants. See our website https://extension.umd.edu/hgic/rust-diseases-trees-and-shrubs

It is up to you if you want to spray next season as a preventative on the serviceberry. To control rust on serviceberry, you would have to start a spray regimen beginning in early spring (March-April). You could use a copper fungicide labeled to control rust. Start the treatments at bud-break and then you will have to spray every two weeks until about June.
There is no chemical control for the junipers. All you can do is handpick the galls. The best recommendation is to select disease resistant plants in the future.
mh