Bronze Birch Borers
Hello, From the title of your note it sounds like you are concerned about bronze birch borers. No they do not contaminate leaves.
Other issues for birch may be happening. Bronze birch borers prefer water stressed trees. Collect samples of the leaves or other parts with symptoms and take them to your local Master Gardener office. https://extension.wsu.edu/benton-franklin/mastergardeners/