I have a little backyard nursery which includes a few young grafted apple trees. Today I saw a bunch of ants gathering around the top of one of the baby apple trees, and green nodes seeming to pop out of the stem. At first I thought these might be ant eggs. I shooed the ants away but the little green things were harder to get off. Upon closer inspection, I think the green things are some sort of aphid but am not sure, but they're not ant eggs at all. Photos at end of post.
What course of action should I take to protect the apple tree (and other trees if applicable)?
When I thought they were ant eggs I considered pruning off the affected area, but hesitated since it's one of two main terminal shoots. Knowing it's not eggs, but rather creatures I can pluck off, pruning seems less appropriate. I've used a neem oil / water solution before with success against pests indoors, so I'm considering that option too. Lastly, I wonder if having so many trees close together matters? I've seen other nurseries put potted trees in groups by species so I figured it's fine, and I have a nice amount of diversity on the lawn and of potted trees on the pallets so I'd hope that'd help prevent any bad pest problems.
Some context and photos:
The apple trees are potted using fresh (from a bag) potting soil with wood chips on top. I keep them, and other potted young trees, on wood pallets in a small yard that gets partial sun or shade depending on location.