Pine trees dying
The lower half of branches dying on spruce (likely blue spruce) is a symptom of needlecast a common fungus disease that is so prevalent in Michigan that we discourage the planting of blue spruce. The fungus kills interior needles but leaves so few needles on ends of branches that it may not be enough needles to keep these branches alive. There are fungicides that can be used as described in the following Extension publication: http://www.extension.umn.edu/garden/yard-garden/trees-shrubs/spruce-tree-diseases/rhizosphaera-needl...
Branches that are totally devoid of needles will not come back and should be removed. Spraying in spring will protect new needles just coming out but may only reduce the fungus on older needles. The recommendations call for two sprayings of a fungicide in every spring.