Question
I have a number of phal, orchids that I have to separate because some have
this white airy mold like substance on the stem, leaves, and where the leaves
shoot out.  it is extremely contagious and has moved to the more healthy
plants over the years.  I"ve tried to clean it with a small bit of rubbing alcohol,
and I thoroughly clean the pots with a bit of bleach.  But it keeps coming
back.  The plants will still bud and bloom, but they don't like this stuff.  What
is it and how can I make it stop attacking my plants.  Thank you, this has
been bugging us for years.

Answer
Lynelle, you have a bad infestation of a sucking insect called mealy bug.  Yes, it reproduces rapidly and will be tough to fight. Yes, you need to separate the infested plants from those that do not yet seem to be infested.  I recommend a three stage approach to treatment.  Go to your garden center and tell them you want them to recommend an insecticide effective against mealy bug when used as a drench. (Also get a bag of orchid potting mix) Then, use cotton soaked in rubbing alcohol to wipe off all visible mealy bugs on the plant.  Then, remove each infested plant from its pot and throw out both the potting mix and the pot.  Recheck the plant and use the cotton soaked in alcohol to remove any mealys you may have missed on the first pass.  Next, you are going to prepare an insecticidal solution (using the directions in mixing the insecticde with water).  At this stage you want to use chemical gloves for safety.  Prepare enough solution so you can submerse each plant fully for at least 15 minutes.  Then remove the plant from the drench and place it in a second container to dry.  With your gloves, place the dry plant in a new pot and add new potting mix.  Do not water for several days.

Note that if you can find either "Bayer Advanced Garden" or a newer chemical called "Merit", these would be best.  These are systemic meaning they get absorbed into the plant tissues and is effective for up to 30 days.  Do not apply any insecticide in a small enclosed area where it can be inhaled.  If you can find a spray, you could use that instead of a drench.  If the latter, place the plant into a plastic bag, spray it, and tie the bag shut for a few days.  After removing the plant from the bag, carefully discard the bag after wrapping it in some paper.