Aphids really don't require prophylactic spraying.

Best advice for tree health is to plant it properly at the correct level, water deeply throughout the first year when rainfall is lacking, and to use some method to verify that you are indeed watering deeply enough- like digging down a time of two to root depth. It's that important. Then mulch and keep the weeds away.

Other than being somewhat yucky and with the potential to distort new growth, aphids have no long lasting impact on the health of a tree. If they should reappear, just hose them off with a strong stream of water. You should not need anything more powerful than that ;-)

The only wrapping that might be needed in a zone 7 is protection from deer or rabbits.

As noted, your primary concerns should be that the tree was planted correctly and receives adequate water its first couple of seasons in the ground.

If you spray with hort oil in warm weather, you will burn the foliage. Just wash off the aphids with water (or learn to ignore them, even better).