First things first, be sure of your identification. Spider mites are pretty easy to identify. They like to hang out on the underside of leaves, and they make a fine webbing that can cover much of the plant in heavy infestations. First signs of spider mites are a light speckling of the leaves, almost like reverse color freckles. One of the more common mites is the two-spotted mite, which can easily be indentified by eye or with a magnifying glass. Here's a couple pics of the 2-spotted spider mite:
Control:
Mites love hot and dry conditions. Obviously, most of us can't move our hops into the shade, but for those who can, that is an option that may help a little. There are also many chemical controls available. One must take care not to spray with any pesticides that are not labeled for food crops. In addition, I would avoid any chemicals that are labeled as systemic, unless you know what your doing and are certain they are safe. Make sure you read the label carefully before purchasing or using any product.
For those who wish to be organic, things are more difficult. My suggestion would be to use a organic insecticidal soap. While less effective, it can provide a modicum of success as long as you spray every-other day. It is important to make sure that you achieve adequate coverage of all surfaces of the plant, especially the undersides of the leaves. The soap will only work if it actually contacts the bugs. I would refrain from spraying with ANYTHING within about 4 days of harvest.
I have also heard of people making a steeped tea out of cigarette butts. Nicotine is highly toxic to most insects yet it degrades rapidly in the sunlight. However, I'm not sure about any lasting smell or flavor impact of this method. I doubt that it would be organic either, unless the smokes you used were organic. I have no experience with this though and cannot recommend a process for making the spray.
Good luck
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