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Plant Diseases/Orchid - spots behind flowers, and on stem


Orchid spots
Orchid spots  

Orchid spots, close up
Orchid spots, close up  

If you could help me identify what these mysterious dark spots are, I would be thrilled. I only noticed them yesterday, and was quite startled! I've had this plant for a few years now, and have kept it in the same spot perched in front of a window. It flowers consistently and stays indoors. Any idea what these spots are, how they got there, and what I can do to fix it? I only see the spots behind the flowers and the part of stem near the flowers; the leaves look great.

Thank you so much, Melissa! :)

Dear Sarah,  Unfortunately, your orchid has scale.  Scale is an insect that is unmoving in its adult stage.  Somehow, you must have carried in some of the nymph stage crawlers, and they developed on your plant.  Scale is a difficult to kill insect using standard insecticides, since the hard covering over the actual insect protects it from insecticides.  Generally, to get rid of scale, I would advise you to spray the plant with horticultural oil, because the horticultural oil (NOT vegetable oil) will coat the hard protective covering and smother the insects.  When you do that, then the bug will dry up and the scale will fall off.  HOWEVER, you have an orchid in bloom, and it would be a terrible shame to waste this.  Get Q-tips, dipped in rubbing alcohol.  Rub each one of the spots with the rubbing alcohol to dislodge them.  It will be time consuming, but the results will be well worth it.  Continue getting each spot as long as you have them.  Be sure to check the underside of the leaves, as they will likely be there also.  When the flowers are gone, you could spray with the horticultural oil.  It won't hurt to give the plant a drench with the oil, in case the roots become affected.  Be very diligent with this insect, because the scales will suck the juices out of the orchid and eventually kill it.  I wish I could explain how scale or mealybugs suddenly show up in the 14th floor of a large office building, but somehow bugs like this will find a way in.  I'm sorry to be the bearer of bad news, but I'm absolutely positive that this is scale, and I'm absolutely positive that these methods will eradicate these bugs.  It will only take some time.  Let me know if you need more help.  Good luck, Melissa

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Melissa Johnston


Plant diseases, landscaping, tropical plants, roses, herbs, plant care, grafting, horticulture, plant identification, anything about plants I can likely answer.


35 years experience in various plant businesses, 1984 Certified Texas Master Gardener.

Master Gardener Association of Texas charter member

none as of yet, but I have a plant q&a book I am in process of submitting.

Magna cum laude graduate of Texas A&M, 1978

Awards and Honors
Plant growing awards, highest grade for Texas Master Gardener graduates.

Past/Present Clients
Past member of and was very highly rated. Owned landscape company in the past, Almost Paradise, and was very successful despite little equipment, no help, and no advertising. Lived well for two years until 9/11.

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