I had same issue with a cutting this winter. The end looked moldy like yours, wouldn't callous up properly, and wouldn't root out. I scored the scion about an inch up from the cut end (in the 3-inch section between nodes) and applied some clonex gel with a q-tip to the scored area. A week later, it's beginning to put out its first signs of a root from within the score mark. This is my first time using clonex, but hopefully it will be a useful trick when I can't get the root end to perform. Good luck. Thanks for mentioning Physan20, Dennis. I remember you talking about this last year and I couldn't for the life of me remember the product you used.