Thank you for contacting Ask Extension. It appears that the bark is falling off the tree. This could have been caused by many things such as natural causes, sunscald, frost cracking, insect infestations, fungal diseases or environmental problems. It could have originally been caused by a weed wacker. But I do see some holes around the root area that could have been caused by insects or a sapsucker/woodpecker. Without a sample, it is hard to determine if it is a fungal disease. I would suggest contacting an arborist Find an Arborist | TreesAreGood.org . Your question requires an on-site visit and evaluation by a tree care specialist, a certified arborist. Regrettably, I cannot provide an effective answer to your question via the limited information provided above. 

Since the tree is 80+ feet tall, it would be easier to have an arborist check it out and see what the tree needs. There might be other problems that they could see that you are not seeing.

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