The safest way I have found is mix rubbing alcohol mixed 1/2 with water and spray the plants 2 or 3 times a day for bad infestation then every other day to take care of any eggs that might hatch. The alcohol kills spider mites on contact then evaperates to leave nothing on the plant or buds. I clean off the webs and look for new webs after spraying it make them easyer to see.