The best thing to use is Ivory soap cause it doesn't have added chemicals. I used a mixture of Ivory soap water (let the bar of soap sit in water overnight) & Canola oil to save my "eaten almost to death" Hibiscus. It recovered & has grown, with no probs, for 2 years since I treated it! A faster way, with the soap, is to just rub it with your hands in the water (faster than the overnight thing).
Leave the soap spray on for an hour or two then wipe it off of the plant (gently) with a damp cloth. If ya dont wipe it off, it can burn the plant (brown).
Ya dont really need to spray the corm or roots. If the plant is out of the pot, go ahead & re-pot it. It may be in a little shock but could still survive. The spraying should be done 2-3 times a week till the mites are gone.
Btw, Bob's right about the humidity thing and about Not freezing the plant to kill the mites. Freezing never helps to kill the mites. If you've got 2 1/2 inches of green stem then you're still doing really good. Even if the whole stem dies, the corm can send up another one. I know this from experience. My baby Sikkimensis died (the whole top) and looked dead for about a month. It was working on growing it's corm, underground, and finally sent up a very healthy new stem with big leaves
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Be sure & keep it warm (above 60 degrees F, 70 would be great) and only water it once a week. I watered my "dead" Sikkimensis only once every 2 weeks & it did Super!
Spider mites can take a whole season to get rid of so Definitely keep the other nanner plants isolated.
If there's something I haven't answered yet, let me know
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