I have several ornamental container trees on my balcony, a red plum, cherry and a weeping pussywillow. Over the summer we had an outbreak of spider mites, which we kept mostly in check with neem oil and another pesticide that I have forgotten the name of.
Well now it's autumn, and starting to get cold, as Germany does. I want to move the trees indoors over the winter, but am afraid of the mites spreading to my indoor plants, which until now have remained unafflicted. I check the leaves, and there are still some mites on the plum, and a tiny bit of webbing.
I would like to know if I could leave the trees out to freeze off the mites? How cold can these sorts of trees get before they are damaged? When can I realistically expect the mites to be dead & gone enough so it would be safe to move the trees indoors?
The seasons have been decidedly mild here, summer only hit to about 33C (90F) and last winter was never colder than -1C (30F), and no snow. If this winter is also as mild as last, can I then leave the trees out later, potentially through the whole winter?