Blue Spruce trees turning yellow
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I have searched various sites for tip die back. One of the biggest spruce problems in Colorado is spider mites. Please look at page 5 of this link for more ways to determine if spider mites is the problem.
I do not see any gall damage from your picture. Also, rrom your picture, spider mite webbing is not noticeable, but may be present with a closer examination. You can test for spider mites throughout the growing season by tapping a branch over white paper and watching for any tiny moving specks.
Also, please examine from the tip of the branch up to older growth to see any discoloration or enlargement of branch tissue indicating any canker.
If you see no traces of spider mites, please send another question and we'll investigate further. The damaged/dead tips can be removed, and should be put in the trash, not composted.