After 3 years of enduring spider mites in my garden, I can finally say I think I found a way to get rid of them. Or rather, to prevent them. I had done lots of research over the course of a year, and then I found an article in the L.A. Times about how the Huntington Gardens handled their spider mite problem. And the weapon was: Water!
Yes, I blasted the undersides of leaves AND watered my plants from the top. What did I have to lose? The mites got my plants all the time by sometime in July. I had tried everything: neem, soap, food grad DE spray, different insecticides, or a combination of all. Nothing worked and I worried as I read that mites only get stronger after spraying. Plus these methods were killing the beneficials too.
Disclaimer: my method worked for me as I only had about 25 plants to tend to. I also planted early, in late March but I think I will go back to April next year to avoid thrips which killed about 3 good plants.
. I set my nozzle to the Flat setting, and sprayed sometimes daily when hot, otherwise maybe twice a week. The weather is hot and dry here, so I tried to replicate the humid wet conditions spider mites don't like.
My season is over but I am doing fall tomatoes now. The tomatoes in my office garden are covered in mites now as I didn't do the water spraying there. So I am hopeful that this simple water spraying will be effective from now on. To me it is the best method yet--cheap, easily available, non-toxic, and easy. No mixing, spraying etc. But it must be done from the very early stages of growth. Spider mite eggs might be in the soil and the adults can also appear on the wind.
Just wanted to post this in case others might want to try it. I am just so happy I had no spider mites on my tomatoes this year. Yes they are on other ornamentals but I did not blast those with water.