Spidermites can cause a disaster if you don't stay on top of them. I've had them in the past and know from personal experience. The best natural way to combat them is to raise your humidity level as high as possible and spray the plants down with Neem Oil. Some folks swear by the "No Pest Strips" you can buy, however I'm not a fan of exposing something I'm going to inhale into my lungs to harsh chemicals.