I think it has golden canker- I will trim but is there a spray ?
If indeed your Pagoda Dogwood (Cornus alternifolia) has golden canker (Crytodiaporthe corni) then pruning off infected branches is the only way to go. Unfortunately there isn’t a spray you can use. In fact the Ontario legislature passed the Cosmetic Pesticide Ban Act back in 2008, which amended the provincial Pesticide Act to ban the use and sale of lawn and garden pesticides. Today there are more environmentally friendly products on the market but in your case they are not likely to be effective.
The following website has some relevant information which you should find useful.