When trimming a maple tree this spring, do I need to cover the cut with anything to keep out bugs or disease?
If you can wait, delay pruning maple trees until late spring or early summer. There is a lot of sap moving through the tree and it is very difficult to prune without tearing the bark during spring. You will also notice a lot of sap "bleeding" from the wound. In general avoid pruning between the time of bud swelling (which they already are) and the leaves fully emerging. Once the leaves are fully emerged, go ahead and prune maple trees. You don't need to cover the wound with anything to keep out bugs or diseases. Extensive pruning should be done in winter when maple trees are dormant.