Hello

Thanks for your question.  Can you possibly take a few photos and upload to this site, so that we can make a better diagnosis for you?  Please take a photo of the entire tree and some close-ups of the leaves and/or any other symptoms that may not be normal.

Hello, 

I am so sorry to ask you for more photos, but the second photo that looks as if it might hold some clues is out of focus and thus not much help.  If that photo is showing holes that are weeping sap, it could be that your tree succumbed to an infestation of hickory bark beetle. Under the bark you would see the characteristic tunnels if this was the case.  If the tree has not leafed out by this point, there is no hope for the tree.  Here is more information on this insect. 

 http://www.misin.msu.edu/facts/detail/?project=misin&id=244&cname=Hickory%20bark%20beetle

When the tree is taken down, you should burn or bury the wood to avoid providing a breeding source for the beetles.  If you want to use the wood for firewood, you should tarp the wood with thick plastic sealed at ground level with dirt around the edges.  Once the wood is thoroughly dried it poses no risk.

These beetles typically attack trees under stress, so take steps to reduce stress on your trees.  This summer, it may mean watering mature trees that we normally do not need to water. Here is information on how to properly water mature trees:

 Watering established trees and shrubs | UMN Extension

If you would like to upload more photos, I would be happy to look at them to see if they fit with what I think I am seeing in the second photo.

Thank you for contacting Ask Extension.

Ruth

Hello,

Thank you for the additional pictures.  The fourth photo in particular was very helpful.  It shows a "target" canker which is caused by a fungal pathogen called Neonectria. See more information in the following article.  https://ag.umass.edu/landscape/fact-sheets/target-canker-of-hardwoods  I suspect that this may have started the slow decline in health of the tree, and bark beetles took advantage of the stressed tree which finished it off.  The best way to protect other trees is to make sure the wood from this tree is treated like I recommended above, and to avoid stresses that you can prevent.  This includes watering (see above article) during drought, and proper pruning techniques.  Trees are best pruned in the late winter or very early spring when dormant.  This avoids pruning when lots of fungal spores are available to infect wounds.  It is also important not to cut into the trunk when removing limbs, as that can create wounds that have a hard time healing properly and can lead to infections.  Take a look at the following manual for general tree care and some good tips on proper pruning. 

https://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5368392.pdf

I hope this answers your questions.  Thank you for contacting Ask Extension.

Ruth