I have tried doing a little bit of research for you and it seems that a lot of spider mites are now immune to Pyrethrum. Seems like neem oil is popular also. But Ed Rosenthal and Harriet Hempster came up with a cool pesticide in his Ask Ed book. Mix a tablespoon each of raw onion, ground garlic, mixed italian seasoning, ground cinamon, and ground cloves, in one quart of boiling water. Mix this with two heaping tablespoons of cornstarch and add 8 ounces od denatured alcohol. It is a powerful general pesticide. Other than that I couldn't find anything else.