Well, I have never dealt with spider mites on plants, but I have dealt with spider mites in general. I have a royal python and snakes have been found to be attacked by the same mites that infect plants, and mine was some years ago. I know that depending on the weather outside where you live, you can use that effectively. I had to get them out of the cage, so I went outside on an extremely hot day and covered my cage with a black trash bag, and let the heat the humidity build up all day and it completely nuked all the mites. Im not sure if there are as many effective ways of getting rid of mites on plants without killing the plants. I also know that cold water (ice water) once a few days a week would probably get rid of them, but the effect on the plant wouldnt be good. Probably a good hosing of water every few days would keep them off? Or just try some effective insecticide. You can try pyrethrum sprays that I have often heard that work very well. Insecticidal soap would also work, and now they even have predatory mites. Spidermites have two commomnly used predators; amblyseius californicus and phytoseiulus longipes. When spidermites are first noticed in your garden, these predatory spidermites should be placed out at about 20 per plant(they must be placed on the individual plant because the predators have a hard time moving from plant to plant), or as many as you feel are needed and repeated once every month there after. To give you a rough idea of how many predators you might need, 1(one) predator mite can eat 20 spidermite eggs or 5 adult mites in a day. Just some information that I had found previously to get rid of spidermites, but I'm in no means an expert on getting them off of plants, may have to ask someone with more knowledge of it then me, but in the meantime, good luck!