Reoccurring mites can be a big problem and a big headache, so I sympathize with your frustrations. And not to add to your frustrations, but during my research on this problem to make sure I got you the best and most thorough solution, I read that depending on how carbaryl (sevin) is being used, it can actually compound and add to the spider mite population! I know, just what you wanted to hear.
I have two recommendations that I believe will resolve your problem. The first and foremost at this time of the season, is to switch to a spray containing Neem Oil. It probably won’t be called that on the shelf, but the product containing that as an “active ingredient” is what you want to use. It’s totally organic, and is classified as an insecticide, miticide and fungicide all in one, so it’s a great product. You should be able to find it at your local independent nursery or garden center, but you’ll probably need to ask for it. I believe it’ll be under the Fertilome label at the nursery, or possibly the Safer label at the garden center.
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