Top of evergreen dying
Since you didn't state the species of tree, my answer will be just guesswork. The damage looks like due to an insect, possibly a sawfly or budworm, rather than a disease. I'd have to see the needles close up to do better than that. But this diagnostic site might help you:
Thank you, unfortunately I don't know the species. If it is sawfly or budworm, what should I use to try to stop it? The website you referred to didn't mention management. Thank you, I appreciate your help!
Given the location of the damage (at the top), I don't think there is much you can do. Read here about spruce budworm:
And here about sawflies:
But you should make sure that that's what the problem is. You'd be best to get a certified arborist to look at your tree: