Question
I am a new orchid grower, and I have a Dendrobium orchid.  It is currently in bloom, and in the last week the stems have started to develop this flaky brown material on them.  It kind of resembles dead skin.  You can remove it by hand, but it takes effort, and the stem is a darker green after it is removed.  What is this and what can I do about it?  Thank you for your help.

Answer
Hello Beth,

While I can't be sure without seeing it, I believe what you may be seeing are scale insects.  Scales have a protective coating over them sort of like turtles.  You can try using isopropyl alcohol on them but that only works on the ones that are visible, not the ones still in the potting mix waiting to come up.  A better solution would be to get a systemic insecticide recommended for scale and use it according to directions.  Go to your local garden center and ask the for a recommendation along with some instructions on how to use it.  Be sure to follow the safety and handling instructions too.  

Scale are very destructive and can slowly kill your orchids as their population increases.  

Hope this helped.  

Jim Kawasaki
San Jose, Ca.