We have a small urban backyard garden in Toronto. Our pagoda dogwood died of golden canker. Our serviceberry has rust (probably related to neighbouring juniper).
We would like to plant a flowering shrub in the spot where the pagoda dogwood grew: a semi-shaded position, w wet, clay soil. We are thinking of a chokeberry shrub. Would the chokeberry (Aronia melanocarpa) be susceptible to golden canker? Would the fungal spores still be in the ground? Would the chokeberry be susceptible to the juniper rust?
Any help would be greatly appreciated.
Sorry to hear you are dealing with golden canker and what you believe may be cedar-apple rust.
Both of the diseases you mention are fungal diseases that infect quite specific hosts. Golden canker is specific to pagoda dogwood (Cornus alternifolia) and is not known to infect other shrubs. Cedar-apple rust requires plants from two different plant families to complete its life cycle. These two plan families are the Cupressaceae family (cedar, juniper) and the Rosaceae family (crabapple, serviceberry).
Unfortunately, chokeberry (Aronia melanocarpa) belongs to the Rosaceae family. If your serviceberry rust is, as you suspect, cedar-apple rust, chokeberry would be also susceptible.
If you still wish to plant a chokeberry shrub, there are a number of things that you can do that will help prevent and/or manage rust and other fungal diseases. These include: looking for rust resistant varieties when selecting shrubs; inspecting shrubs for signs of disease prior to purchase; watering shrubs at their base rather than from above (rust requires water on the leaves in order to grow); watering early in the day and ensuring good air circulation to help keep leaves dry; inspecting shrubs regularly and removing and disposing of infected leaves or branches.
If you would prefer to look for a different type of shrub (i.e. one that is not a member of the Rosaceae family), the Toronto Master Gardeners Gardening Guide on ornamental shrubs for different light conditions lists many shrubs that you might consider.
Ornamental Shrubs for Various Light Conditions; A Toronto Master Gardeners Guide