Is this a bacteria or fungus?
 

This has appeared on a few of my Dendrobium canes.
Attachment 68003

I don't know but my first guess is always fungus. Do use Physan 20 at all? It's both a fugicide and a bacteriacide, but it's not very strong. Sometimes you need something stronger.

I have it but have never used it. I've been spraying every weekend with cinnamon extract, water and dish soap. Not so sure that kills bacteria and fungus though, lol...