I have 2 maples that have gotten some trunk problems out of nowhere. The first is a sango kaku that was perfectly fine, and then I noticed the bark right near the graft peeled off as seen in the picture. About a week after noticing this, the leaves have all dried and shriveled up. I dug it up and potted it because I wanted to see what the roots looked like as well as put it in a more sheltered location to see if it would rebound. The roots were fine, showed no signs of overwatering. There was a big red ant nest that I disturbed. (Don't know if that has anything to do with it) Then today I noticed the same thing developing on my Autumn Blaze maple which is about 15 ft from the sango kaku. So far the leaves are fine on the Autumn blaze, but I'm afraid the same thing is about to happen. Is this some kind of fungus, or insect issue such as a borer? These trees are both fairly young and have been in their current spots for about 2-2.5 years. Autumn blaze is about 8 ft tall, and sango kaku is about 5 ft tall. Thanks for any input.

Sango Kaku

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Autumn blaze

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