One method is to find a large tub that the whole pot will fit in. Fill it with water and submerge the plant, and the pot in the tub. I have never done this, and I would think you may lose some soil. But many gardener's do this. Keep in there for 5-10 minutes. Any bugs will die. The plant will be well watered, but should be fine! No chemicals!
I live in MI and I usually bring my pots in very late just before frost, and most insects have left or are dead already.

Thanx

I was planning a series of hort oil sprays for the leaves and trunks but was stymied by what to do with the soil.

Mike

The problem I have every year is spider mites, which seem to be inside pests, not outside, at least I never see them while the trees are outside. Spritzing them regularly with water helps keep them off.