Neem oil. Spray on leaves in veg, getting top and bottom....Leaves will get a waxy shine and then they don't need more.

Spider mites are not killed by neem, they can't eat the stuff as babies. So you kill off the hatchlings. The adults just live out their lives and die.

I had a horrible infestation about 2 years ago. Learned prevention is much easier and less costly than chasing them down as an infestation. Treat the plants from about 2 weeks in veg until they are into flower 2 weeks.

Use a good deterrent poison outside the grow area and at the air intake(s), I use Sevin, once a month, just a simple spray a line around the perimeter of the room.

I have not had mites since I began this process. In non-mite season, I drop the foliar spraying of the neem, but make sure that at least 2 months before the season the plants are being sprayed as they will uptake some of the neem and it will be systemic.

Neem comes from a tree. Non-toxic to humans.