London, but hoping you can help. Tree has been losing leaves since spring. Planted in heavy loam but near slope. Full sun. Large cedar hedge across street. Tree is in lawn. Have had considerable heat and humidity/rain this season.
Serviceberry blight, rust fungi, or both?
What measures can I take to help tree? It was planted by my mother (former local Garden Club president) to support the Carolinian Forest. Very precious to me.
Thank you for reaching out to Toronto Master Gardners.
Although we are seeing trees displaying canopy issues due to the heat, the issue you describe is likely more fundamental, as the leaf drop started in the spring.
You possibly considered Cedar-Hawthorn Rust, as you commented on the proximity of cedars. The symptom you describe is consistent with this. To confirm it, you could consider examining the leaves that are dropping. Infections of Serviceberry from this pathogen are quite distinctive. Circular, yellow to orange spots appear on upper surface of the Serviceberry leaves after bloom in late spring, turning into black raised dots forming in the centre of the spots on the upper leaf surface.
If this diagnosis is correct, the infection does not generally damage the tree.
Here are some links that are hopefully useful and may provide insights if you rule out Cedar-Hawthorn Rust.
https://portal.ct.gov/caes/plant-pest-handbook/pphs/shadbush-serviceberry-amelanchier
Prior Toronto Master Gardener answers that addressed the same or similar issues:
https://www.torontomastergardeners.ca/askagardener/serviceberry-4/
https://www.torontomastergardeners.ca/askagardener/serviceberry-rust/
London does have their own Master Gardener program. Here is the link:
https://londonmiddlesexmastergardeners.com
Thank you again for contacting Toronto Master Gardeners and I hope your beautiful tree comes back in full strength next year.