All the people having spidermite infestations are missing the obvious,if you make the enviroment unattractive to them they wont get a foot hold in your grow,i had spidermites once,once & thats it.
Increase air flow over,under,around & thru every last plant until every last leaf flutters & thats all you have to do,no shit its that simple,if the leaves have enough moving air the spidermites cant latch on.
A friend of mine who runs several greenhouses showed me this & its been years since ive had a single mite & ive been in a half dozen grow ops that had them & never transfered them to my grow.
Get those plants moving in the breeze & forget about mites forever.