I wasn't paying attention to a Green Gauge plum tree in the corner of my orchard until I noticed that, in it's fourth year, it had very small leaves and was shooting up lots of suckers. I removed the plastic tree wrap and discovered that some sap had dried and glued the tree wrap, thereby creating a tourniquet around the trunk. It's removed now, but the trunk has a noticeable hourglass shape and some of the bark in that area doesn't look healthy. The tree is still alive, and actually produced some small plums this year which were pretty good.

Will the tree recover? The trunk is about 2 inches in diameter and narrows to 1.5 at the spot.

I cleared the ground all around it and heavily mulched it. Anything more I should do? Extra water or fertilizer? It's already dropped a lot of it's leaves, and the remaining leaves are small, but the branches and twigs are all still alive.