An excellent recipe for a natural, homemade spider mite treatement, courtesy of CannibisCulture.com, a treasure trove of useful gardening information, no matter what you're growing:
To each quart of water, use a tablespoon each of ground cinnamon, ground clove and 2 tablespoons of ground Italian seasoning. Heat the mixture until it starts to simmer, then turn off the heat. Add 2 tablespoons crushed fresh garlic when the water cools to warm. Let the tea sit until it cools. Strain and save the water using a cloth or coffee filter. Add a few drops of liquid soap or dishwashing liquid to the water.
Pour the tea into a spray bottle and spray the undersides of the leaves. Use every three days for two weeks.

 
 
