Orthene. The powder, not the oil. Tablespoon to the gallon. Repeat in 2 weeks. It will kill on contact and systemically. Bayer will work but I hesitate as there is 3 different poisons, 2 you don't need. Orthene is relatively benign. But still be careful. It stinks. Can be mixed with fertilizer. Very effective. Safer soap or ivory would do it but not as effective. Don't treat inside your house.

Since you are indoors , I would stick with insecticidal soap. You can also try some rubbing alcohol mixed with water in a spray bottle. Alcohol dissolves the wax coating the adults use for protection. The soap or oil spray will kill them in the crawler stage. This will keep them under control until spring when you can hit them with a systemic outside.

Keep treating even if you don't see them because there will always be some hiding in sheaths or in the bark. Neem oil is good to use because it also has some anti fungal properties, and you can get it in concentrate so you can mix your own which will be cheaper. I have been seeing cedar oil based sprays lately, I don't know if they work any better but they do smell much better.

Maybe next year spay systemic 2 weeks before you bring them in and the day before....

Thanks everyone. I have to treat indoors, unfortunately, so since I also have Neem oil concentrate I think I'll start there.

I agree that spraying with a systemic before I bring them in is a good plan. I never have much notice though as our autumn weather varies wildly and then one night it gets COLD and I scramble with bring everything in. Some years that's in October (this year) and some years it's in December (last year).

I use Bayer All in One Rose and Flower Care Bayer All in One every fall on most of my orchids. 3 separate treatments over a 3-4 week period prior to bringing them in for the winter. A few years ago I used it indoors during the winter here in Ohio, I did take the orchids to the garage on a warmer day and treated them there.

I find mealies on multiple plants very tough to get rid of without a systemic. I've only had scale issues one winter @10 years ago and it was a real battle to get under control, but that was before I used systemics.

Good luck,

Bob