Hi,
In my own orchard, I would plant citronella - it is hardy in Zone7. You could plant it all around each tree.
I have some "bushes" of citronella all around the garden.
That plant is a weed so from year to year it sprouts here and there. I let them grow.
When the bushes are too big, I cut them . I have mint around... That seems to help as well with mosquitoes .