Thank you for asking Extension about your Dogwood tree.  The picture is definitely showing that the tree is having some problems, but it is difficult to know exactly which one is causing the leaf curl and brown spots.  Trees have a limited way of responding to various disease/pest conditions--insects, viruses, fungi, bacteria, and even weather issues can cause similar symptoms on a tree.

The yellowing of the leaves (chlorosis) may be a sign that the tree is not taking up enough nutrients (eg iron, magnesium, manganese, boron) to let the chorophyll work properly.  A soil test --check with your county extension office--would be the place to start with that.  Nutrient issues can be complex--even if the nutrient is in the soil, if the pH is off the plant may not be able to take it up.  Sometimes an excess of one element blocks absorption of another one.  An unhealthy tree will be more susceptible to diseases and pests.

One group of problems common in plants this year, caused by the damp early spring conditions, is caused by fungi.  My thought, based on your picture, is that anthracnose fungus may be the cause of the brown, curled leaves.  Submitting a sample to the OSU plant diagnostic lab might give you an exact answer (see link below).
Submit Sample | PPDC (osu.edu)

Here are a few other sites that have good pictures and descriptions of Dogwood issues:
Dogwood Diseases (psu.edu)

This one has great pictures of various Dogwood leaf diseases, including anthracnose.   
Dogwood: Identify and Manage Problems | University of Maryland Extension (umd.edu)

This one goes over diseases of Dogwoods with pictures and management information
Dogwood Diseases & Insect Pests | Home & Garden Information Center (clemson.edu)

In general, control of fungal disease requires cultural and chemical measures.  Improving air circulation by thinning the tree, making sure it has healthy soil, and judicious timing with use of approved fungicides are all important.  Many fungal issues are secondary to the weather patterns and only cause mild problems for a tree that it can overcome on its own. Some varieties of trees will be resistant to specific fungi; for instance, Dogwoods that are resistant to anthracnose include Kousa, Red Osier, and Tartarian.

Sorry this response is not very specific; there are too many things that can cause the symptoms you are seeing.  Take a good look at the photos in the links and see what seems to match your tree's symptoms the best, and consider submitting tissue to the diagnostic lab for a good answer.