Mites (not spider mites)...?!

[estación seca]

I use alcohol 70% OR soap. Rubbing alcohol as sold at drug stores is usually 70%. Sometimes it's 90%. I have used 90% only on warm days so it evaporates quickly.

In a coolish, humid environment I would probably use the soap first, so the alcohol didn't linger to kill the leaves, but I don't have that. I use alcohol for smaller applications, and soap for larger, due to the cost difference.

Edit: I use isopropyl alcohol 70% because lower concentrations didn't reliably kill them. I use isopropyl alcohol because that's sold at every drug store and market in the US, and cheap. I think rbarata uses ethyl alcohol because isopropyl is hard to buy in Europe. There might be a difference in killing between the two but I haven't compared them.

The only ethanol sold in the US to the general public is sold for human consumption. (There was at one time a famous goat at the store in Big Bend National Park that would drink beer offered by tourists. It held the bottle in its lips while tipping it up.) Ethyl alcohol in the US is very much more expensive than isopropanol.

[rbarata]

Here the commonly available alcohol is 90%.
In practice I don't follow the 5% ratio. I just pour a small amount of alcohol because I know even in a small amount it will kill most of them. Those that won't be affected by the alcohol, they better be very good swimmers.

[Dollythehun]

I used 90% that might have been my problem.

[rbarata]

You can use 90% without any problems as long as you compensate for the extra 20%. Dissolve 20% less from the 5%, i.e., 4%/liter.

[Ornery Orchids]

I didn't read every single post in this thread but they sound like beneficial predatory mites to me. If ever in doubt though, and if you are located in the USA, you can take a plant to your local agricultural extension office and they can get you an ID on any pest or disease issue. It takes the guess work out of it. Sometimes it's a free service though if they have to send something to a lab, there will be a small fee.