I have a 7 year old cornus kousa which is now 10 ft tall. It is nestled in my Toronto backyard, facing west. Sadly this year it did not bloom at all and recently some leaves are already beginning to change colour. Importantly, today I noticed orange dots, which in can scrape off with my finger, isolated to an 8 inch limb which had been pruned back in the spring from winter damage. I have pruned this out, disinfected my pruners and put the limb in the garbage. Is this golden canker? Any help restoring my beautiful dogwood back to health would be much appreciated!
The Kousa Dogwood generally has better disease resistance and better cold hardiness than flowering dogwood, and is an excellent alternative to flowering dogwood (which is susceptible to anthracnose). That said this certainly looks like the fungus Golden Canker.
This is a very good website which will inform you of the biology of the fungus and next steps for management.
I would recommend you find an arborist to have a closer look at your tree , & positively identify the problem.