Diseased crab apple
You can send us photos of your dogwood tree, spots, and trunk so we can see what you are referring to.
The tree in the photo looks like it may be a crabapple tree. They can be susceptible to several fungal diseases. This looks like a rust disease on the foliage. Rust diseases have a complicated life cycle in that two types of plants, a pomaceous plant (apples, pears, serviceberry/shadbush, quince, and crabapples), and a cedar in which to complete their life cycle. This disease is unattractive but does not kill the tree. This can be common in moist spring weather. Rake and destroy any fallen leaves and fruit. Read more about it on our website. https://extension.umd.edu/hgic/topics/rust-diseases-trees
We do not recommend trying to control rusts on ornamentals with fungicides. In the landscape, damage to either host is not severe enough to warrant fungicide applications. Fungicides are preventatives and would not cure what is already there. They only protect new or uninfected foliage.
It is recommended to purchase the most disease resistant varieties in the future. See the attached links http://www.clemson.edu/extension/hgic/plants/landscape/trees/hgic1007.html