There are many things that cause spruce decline and needle drop. It's going to be very difficult to pin this down with just the one photograph.
I'd start off by downloading and reading through this article on Spruce Decline from Michigan State: http://msue.anr.msu.edu/news/what_is_spruce_decline_and_what_should_you_do_about_it . This article has some good pictures, and lists numerous possible causes for the symptoms your picture is showing.
As you read this article, please review everything that has happened in your yard over the past year or two. Have there been any herbicides used on the lawn, or under the spruce trees? Has there been periods of drought in the last couple of years? What was the weather like this past 12 months?
To check for spider mites: go to a branch that is BEGINNING to look sick (not a dead one). Hold a sheet of white paper under this branch, and smack the branch a couple of times. If there are mites, they will drop to the paper and begin crawling slowly around. If you examine them with a magnifying glass, you should see tiny critters with 8 legs. If you see that, let me know and I can recommend some treatment options.
You may need to send samples to the Univ. of Illinois Plant Clinic to have the causal agent identified: http://web.extension.illinois.edu/plantclinic/ . I don't know what they charge for this service, but their website should have the answers.