Question
Hi there,

I own about six orchid plants - all of them have lost their petals except for one a "phalaenopsis - long pride star". I noticed last week that it had a lot of white mold growing on the back of the flower. I noticed too that the spots where petals had been along the stem also had mold growing and when I investigated the leaves it was there too. I am very nervous that this mold will contaminate my other orchids and this morning I found that another phalaenopsis had the same white mold growing out of the centre of the stem and onto the new leaves. I have never re-potted these plants since I got them - is this what I should do? If I re-pot them can I use the same pot after it has been carefully washed out or should I get a new pot. And finally, how does this awful mold begin?

Thank you for helping me save my orchids,

Vanessa

Answer
That is not white mold Vanessa.  It is a sucking insect called a Mealy bug and will readily spread from plant to plant.  Over time, it will kill the plants.  One of the first places this appears is on the back of flowers where there is a lot of plant sap upon which they feed. It is difficult to say where they came from, but adults or eggs could have been present in the orchid potting mix of one or more of the plants you purchased.

You need to get some fresh orchid potting mix and an insecticide that is effective against Mealy.  Your garden center can help you as there are many products.  I use an insecticide called "Eight".  After getting the fresh orchid potting mix, set it aside and, before yopu open it, unpot your orchid plants that show sign of mealy.  First spray off the roots and all parts of the plants with a spray of water from a hose.  Remove any "mushy" roots.  Then let the plant dry and spray the entire plant with the insectcide and let that dry (use rubber gloves).  Repot in a fresh pot ( or as you suggested, a thoroughly cleaned pot) and fresh potting mix (Be sure all sign of the mealy bug are gone before repotting). Immediately discard all old potting mix by putting it in a plastic bag and sealing it. Spraying with an insecticide will destroy any new hatchlings or small insects remaining.  You will need to monitor your plants for a few weeks to be sure the Mealys don't return.  If you had just a very few Mealys you could remove them with a q-tip or cottn swab soaked in rubbing alcohol.  For now, however, it appears that your mealy infestation requires the procedure I outlined above.