I recently purchased some poncirus trifoliata citrus seedlings, and noticed one of them struggling after about a week. Upon closer inspection I found it covered in red mites.
I live in zone 6b, so we get cold enough winters that it will go dormant. I’m wintering them indoors this year and then will plant out in the spring. I’m wondering if the red mites would survive a winter and the plant going dormant.
I’d rather not use any kind of pesticide, so I don’t mind killing them all by hand for this winter and then letting the climate do its work.
Welcome to Permies!
Red spider mite are pretty persistent in my experience. They like hot dry conditions, but seem to overwinter successfully too. I found this site which gives some details on the spidermite identification and lifecycle along with some predatory mite information. It is possible to buy predatory mites by post.
It may be that once the plants have a chance to settle in the mites will rebalance naturally, I used to have problems in my polytunnel, but after introducing predatory mites and a pond and using mulch and trickle irrigation to increase the humidity I don't notice the mites now after a few years. I think they are probably still there, but with better balance.
It might also be worth contacting the supplier of the plants for advice.