Answer: Based on your description I am not certain what has happened to your trees. It is possible that birch leaf miners have defoliated them, it is also possible that borers have contributed to some of the branch dieback. Both of these are serious problems in birches. I would suggest you work with your local county extension and/or a professionally trained and certified arborist who can help you troubleshoot and identify the pest and the cause(s) for the trees not leafing out. Based on knowing that, you can determine how to proceed. I'm sorry I can't be more specific for you.
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