I am sorry for this delayed reply to your gardening question. The spring rush has brought a deluge of questions and we are working hard to catch up!
Prune out the dead back to where it joins living wood. Look for signs of borers such as holes or sawdust near the intersection between living and dead. Hopefully there was just a problem that set the tree back (dry or soggy conditions or physical damage) and with proper care it will be fine and begin to regrow now. If you find borers see your local Home Depot garden center for a spray for borer control. I suspect that this is not the cause but I mention it just to be sure.
Thanks for the question. Best wishes for a wonderful gardening season. Please stop in again soon!
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