cut off an inch from the top. If it is dark or black, cut another inch until you get to green wood. Let dry and hope for the best.After a day you can coat the cut with spackle, tub and tile sealant, water based paint or tree pruning tar. You can just leave it but sometimes this leads to more black tip. Coating it reduces the chances of more black tip but is not a guarantee. If the plant recovers, it will start growing small new branches parallel to the sides or at an angle. Good luck. If you leave it alone, the disease will spread downward. Bill

Thanks, Bill. I wasn't sure if a cutting would grow if the end was cut off--all of the photos I've seen on the Internet show a cutting that includes the end of a branch. I'll give that a try--nothing much to lose!
Marcia

Here is an image of the cutting after taking off the first inch (and the inch piece cut in half). Should I cut another inch off, since there is still some dark showing? If there is still a dark line showing after that, should I continue cutting until only green & white show?
Thanks.
Marcia

I would cut thin slices dipping my knife in alcohol between cuts until that black is gone. You are very close to where it should end.

Thanks again, Bill. The fungus went pretty far down. I probably took off more than half of the cutting and have about 5 inches above soil line left. What will be, will be. Thanks for your advice.
Marcia