Answer: Scale can be difficult to control once introduced in your plant collection. If possible, isolate the affected plant(s) to try to protect the others from infestation. Sometimes it is better to dispose of a badly infested plant rather than try to battle the scale on it, but obviously this is a difficult decision to make.
Horticultural oil and commercially formulated insecticidal soap can be used per the label directions to control them, along with isopropyl alcohol on a cotton swab for spot removal.
If you would prefer to try a systemic, please consult with your local county extension for their specific recommendations. And whatever you use, please test on just a leaf or two for adverse reactions before spraying all over.
In the meantime, you may find the following discussion of scale on orchids of interest. You may need to cut and paste the complete url into your browser to make it work correctly.
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