Hello there. It is hard to tell what is going on with your tree leaves from the photos. It could be leaf scorch which is sun/heat stress symptoms, could be a watering issue or possibly a fungal issue. It would be helpful to know if the symptoms appear on ALL SIDES of the tree or are more prevalent on the south facing aspect of the tree. I think you should bring some samples of the leaves effected to the OSU Benton County Extension Master Gardener help desk so they can see the leaves and if necessary put them under the microscope to look for possible leaf fungal issues. Be sure to bring these photos with you. Be prepared for questions about watering and or soil compaction issues. Perhaps add a photo or two showing the whole tree and where it is planted. How long it has been planted and what type of dogwood it is. What month it blooms in etc. All information you can provide about the tree would be helpful. The Extension Office is located at 4077 SE Research Way in Corvallis. Phone before going to ensure a MG is on duty. Office hours are 8-5 weekdays. Phone is 541-766-6750.
Thank you so much Debbie, for your thorough response. We will be bringing a sample in this afternoon!