Diabetes affects our blood vessels and nerves and therefore can affect any part of the body. However, certain parts of our body are affected more than other parts.
I don't think dogwoods have (much?) scent, maybe just lightly floral. The white petally looking things are not actually petals they are bracts, like a poinsettia has. There's something called an English dogwood that is very fragrant, but it isn't a true dogwood and is also known as mock orange. Bradford pears have a smell that this author described as sweaty socks, so if your tree doesn't smell very good that's probably it: http://www.gardenguides.com/106133-dogw ...
Fungi are the main causes of dogwood tree diseases. Fungi thrive in cool, wet weather and prevention is the best cure. To head off fungal diseases, plant dogwood trees with enough space between them and other plants so that air can circulate around the tree. Check the leaves and make sure rain water does not make little puddles. Remove any infected parts as soon as they appear and dispose of them, preferably by burning.