I've been experimenting with essential oils (rosemary in particular) for almost a year now as aphids and spider mites are an ongoing battle for me here. We haven't had a hard freeze for about 7 years now and all the bugs are at full strength all the time.
The sponge stem barrier is not my idea, I saw it here or on another forum but it's a great way to keep pests from "climbing the tree" as it were.
By the way, the essential oils mixes need to be sprayed weekly to be effective, but for a non systemic, organic solution they seem to be working quite well for me. I can't say they eradicate the pests, but they do seem to keep them in check. Plants are healthy, happy and show no signs of pest infestation even though I occasionally can scope a spider mite or two.