Here in te EU, the most efficient pesticides are controlled substances and can onçy be bought and used by a qualified person (which I am not).
I have found that a friend of mine has all the necessary authorizations to buy those products, but since the ones I used to apply were prohibited, at this moment I really don't know what is the best product to use on orchids.
So, what is the best active ingredient against spider mites?
No, you just spray the entire plant every now and then, being sure to spray under the leaves. It's the only thing I use to control them. There are spider mites outside in my landscape all the time. If I'm gone for a while and return to a plant with a severe attack I use alcohol, but not for regular treatment.
__________________ May the bridges I've burned light my way.