I don't know what is on the tree. It looks like you have mushrooms in your mulch. You'll want to use gloves to remove them, then throw them away in a plastic bag. As far as I know there really isn't anything you can do to prevent mushrooms from coming back, besides making sure you have good drainage.
Those appear to be leaf galls on your hickory tree leaves. I think all you can do once they are there is to prune the leaves off. There are likely sprays to prevent future growth. Maybe get in touch with a local ag extension office for advice.
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