Any idea what’s going on with the rootstock on this apple tree?

[letemgrow]

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[Turkey Creek]

Potentially collar rot. Pull any organic matter away from the base of the trunk you might even pull a little bit of dirt away as well to below the part that is sloughing off. Give it a chance to dry out all the way, the trunk that is. Not sure it will cure it but might help slow it.

 

[letemgrow]

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[chickenlittle]

I'm not sure what it is. I have that on a few trees that are not in locations I'd expect any rot. I'm pretty sure even some of my Geneva's have something like this and they are resistant to crown rot.