Question

Oncidium   I'm attaching a picture of a problem that is starting with my oncidium.  Leaves are starting to turn spotty yellow and I checked under the leaves and small black spots are appearing.  I have it growing in a East/south window with a shear curtain for the sun above the kitchen sink.  I have a wood burning stove, therefore, I mist all my plants about twice per day until about 2p.  Please help, hate to loose this orchid.  It has beautiful, fragrant yellow flowers.

Answer
Grace, this is a common problem with oncidiums. While it is unsightly, it will not cause the orchid to die. This is likely a fungus resulting from the mist settling on the leaves.  There is no treatment to remove the spotting.  I have, however, had good success using a copper based fungicide which you can mist onto the leaves to prevent it from affecting new growth. I also would reduce your misting to early in the morning only and use a small fan to evaporate any excess moisture that may remain on the leaves after misting. When new growth starts, consider repotting you plant in fresh orchid potting mix. Be sure to use a pot with lots of drainage holes and a commercial grade of orchid potting mix.