There are some hanging around and overwintering in various places such as leaf debris, canes, supports etc so plan on seeing them again. They like a dry environment so perhaps misting the plants will keep their numbers down but they are very hard to control and they reproduce at a very rapid rate so pesticides are a no go since they will become resistant to anything you try. Any plant of mine that got hit with spider mite I trashed, perhaps other members will have a solution for you...Good Luck!

I would give the plants a good washing once or twice a week as a preventative, and give them as much ventilation as you can. This creates a friendly environment for predatory mites, which will keep the spider mites down. Neem oil and cedar oil are good organic remedies, as is organic dish soap.

I would say that the biological pest control, parasitic wasp treatment would be the answer. This could prove to be expensive but would work. For the last few years I have been plagued with red spider mite on my greenhouse cucumbers. I have used a sulpher candle in the spring; have kept misting the house down on a regular basis and even invested in 'Plant Invigorator', but to no avail. The wasp treatment would not be worthwhile for me as I have only two plants to deal with.

Parasitoid wasps won't eat spider mites, but there are many other predators of spider mites that can be purchased and released in the polytunnel, and the wasps will take care of any problems you might have with aphids and caterpillars.

You are quite right Tug, not a parasitic wasp but the point I was trying to make was that the biological route was the way to go. Red spider mite can be controlled biologically indoors or outside by using their natural enemy, the predatory mite Phytoseiulus persimilis. Google HELP@DEFENDERS.CO.UK.