At one time elm trees were common in many places in America, but in recent years the elm bark beetle and Dutch elm disease have virtually wiped out many of them. This makes it more important than ever that homeowners top and prune their elm trees with care. Elms should be pruned only in late winter or early spring before the elm bark beetle is active.
Cut out all dead, broken and diseased branches. Make all cuts about 1 inch from the branch collar (the point at which the branch grows out of the trunk or out of a larger branch).
Cut all branches that are growing sideways through the canopy or at a downward angle.
Cut all branches that are rubbing against one another because the rubbing can break the bark and allow the elm bark beetle an easy entry point.
Top the tree, if necessary, by cutting vertical branches 1 inch from the branch collar. The pain trunk can be topped as long as you do not cut more than a third of the tree's height.
Paint all cuts immediately with a tree wound compound or latex paint. This will help prevent elm bark beetle from gaining access to the tree.