I don't have pictures but I have seen more than once of mostly main trunk getting some form of rot. It seems to turn brown then you see a stem coming off, start to die. Everything above the spot starts dying one at a time. I thought it might be some powdery mildew. Not sure but it attacks the whole plant if left. It's there a name for this? I don't see a remedy. I have tried several things to try and cure it but it seems to continue. I have seen whole leaves get dark and get what looks like a black covering or spotting also. Always trying to learn more.