All the new growth leaves are covered on the underside by these tiny black insects and a few of these larger ones.

The leaves are dying - if it ever stops raining I've got some spray to kill them with, just wondering what they are....

That bigger one is a ladybird larva which eats insects, and not plants but I guess just the one won't make a difference!

Once you get it, you are pretty much guaranteed to get it every following year, so advice above is good.

Next year, you can hold off spraying if you want until the first signs, but you have to check all over on a daily basis, they tend to conceal themselves very well, and by the time leaves start curling they are well established. As said above do not spray until blossom is well finished for the sake of bees.

To be honest, their spread is so explosive, no natural predators will ever keep it in check.

It is a matter of personal belief/preference, but I would spray now, or after harvest at least, it will kill the friendly stuff too, but may still allow the tree time to recover and put on a little more growth, and will lessen the risk of canker etc. being introduced.

Read the label on the insecticide carefully as some can only be used up to 14 days before eating.

Just beware that these things never end well. The scientists always die or get infected, and the team sent in to stop the out of control infestation are usually wiped out bar one or two unlikely souls who seem to rise to the occasion.