Posted: 25/07/2015 at 15:34
Try SB plant invigorator which sort of sticks them in place so they eventually die. It also contains a foliar feed to help the plants grow. The only thing I've found truly effective are spider mite predators (Phytoseilus.) The suppliers of those often also recommend SB as an initial treatment before applying the predator mites.
Spider mites have evolved to be immune to most insecticides.