This looks like a Magnolia tree, not a Dogwood tree. The fuzzy white that you are seeing on the branches is not mold, it's an insect called Magnolia scale. 

The other insect on the leaves that looks round and black, may not be anything to worry about, but keep an eye on it and if you see more and notice them eating the leaves, send in more pictures. 

As for the Magnolia scale, right now there isn't much you can do.  In August, you can apply horticultural oil, which can be purchased at any garden center, then apply dormant oil in October/November and again in March to kill the overwintering nymph stage of the insect.

If the tree is small, you can try using a dish scrubber to remove some of the scale, but you will still need to use a horticultural oil in August.  

If you'd like to learn more about the life cycle of the Magnolia scale, Ohio State University has a great article: https://bygl.osu.edu/node/1986

Thank you for your question.