Looks like you have aphids. Do a google search for: aphids control. Or search this site. I can't tell how big your tree is. If you can reach them with a hose, many people just spray them off with a strong spray of water. You can also use an insecticidal soap mixed with water which will suffocate them. They are quite delicate and have a number of predators. In small numbers they won't do any serious damage but they propagate quickly. They like young succulant growth which the drastic pruning and spring combine to make. If you look closely you may notice small shiny drops of clear sweet liquid on the leaves, ground, or whatever is beneath them. They suck juices from the tree and excrete that "honeydew". Ants like it and can be found fostering them.

Help! My apple tree is having problems. Recently I posted about a problem with little black winged creatures on my apple tree. They were identified on this forum as aphids. I have been spraying my tree with soapy water to get rid of the aphids, however they seem to have gotten worse. Although the ants are no longer climbing on my tree to eat them. But now the leaves on the tree are browning. Help. My tree is starting to look quite unhealthy. What do I do?

When we bought this house there was an existing apple. One of those with several varieties grafted onto it. Definitely had fire blight. We tore it out and burned it. Happily it wasn't near the big old Anna. No blight there. I'm glad you found out what the problem was and can start fresh. Good luck with your new trees. I hope your wife is good with apples because you are going to have them coming out your ears! She will need an apple corer, peeler and slicer all in one. I got mine on Amazon and it has a suction thing so it sticks to the counter while it's being turned.

Yes, the pot looks small and the plant looks underfed. You are giving it only about a quarter of its nutrient needs: Citrus Focus instructions say "Add 10ml of Citrus Focus in every litre of clean water, weekly. If leaves are pale or yellow, increase frequency of application."