I have a peach tree in my polytunnel and it has had a growing red spider mite infestation over the last couple of years to the point where it is debilitating to the tree, which is almost bald. I can't use insecticide even if I wanted to as the main problem occurs when there is fruit on the tree. I've spent a fortune on parasitic wasps as a biological control, as that is the most often quoted solution. They check the population growth, but the numbers climb again in a couple of weeks. Does anyone have any experience of using non chemical sprays, like garlic? I'm trying one with garlic, vegetable oil and chilli in it that sure scares me out of the polytunnel, but I don't know about the mites. I'm open to all ideas on this one!
Would it work to plant an insect repellant plant like wormwood under the tree?