Answer: The first line of defense in your yard is keeping the grass and weeds mowed. This gives them fewer places to hide and promotes air circulation and sunlight penetration. Apply a formulation of horticultural oil and water. If you don't know what to use, ask your nursery for dormant oil, which is the same stuff you spray on your fruit trees in the spring. Use the summer formulation. Some soap (such as Dawn) may also be added as a spreader. Spray at the recommended rate. Try to do this on a cloudy day or in the evening. Burning of foliage may occur, especially if it has been hot and dry. Do a small test spot if you are unsure and adjust accordingly. The oil (and/or soap) will smother the mites and severely limit numbers available for reproduction.
You can also use sulfur dust (aka flowers of sulfur). Use the recommended rate. The action here is that sulfur dioxide (SO2) is formed by oxidation in the presence of sunlight and kills the pest. The sulfur will also kill other insects, possibly the beneficials as well. Do not use oil and sulfur at the same time, unless you want to kill everything.
Hope this helps.
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