With the nightly temperatures dropping to the mid to upper 30's on a regular basis, I scramble to bring in my formidable collection of houseplants that have been enjoying their days outside. Inevitably there are always hitchhikers hiding on the leaves and in the soil that find the conditions inside the house quite pleasing indeed (high temperatures and low humidity). Before you realize it, you have an outbreak of white flies or spider mites (pictured). I have battled spider mites on a couple of my prized citrus trees and never really win the battle– only control. They can easily take a plant down in three weeks or less if not kept in check.
I'm very weary of using harsh chemical insecticides since the citrus trees bear fruit and I plan to eat them. So I've always used just liquid hand soap that I've had (last year was Johnson & Johnson Baby Soap).
This year I have some new tools. I picked up Dr. Bronner's Magic Soap, a 100% vegetable-based castille soap that folks have claimed it works well as an insect soap. Today was the first application. I'll post an update in a couple of weeks. (Warning: the bottle of Dr. Bronner's Magic Soap is highly dense with text; may cause dizziness). A good spray bottle is also essential for treating your plants. Home Depot has a nice Zep Professional Sprayer for about four bucks.
Link.