Hi one of my coleus developed a white mold on its stems in the summer. It didn's seem to affect it too much, I cut off the mold parts but when I brought all different coleus in the house in the fall, they all developed the mold on their stems and it killed them all. Now it is on my Hoya and it is a pretty tough old bird about 50 years old, well the original one would be. What is this and how can I get rid of it. Doesn't seem to affect geraniums or Ivy or any of my succulents.