Needle cast in blue spruce
When people say needle cast, they are usually referring to Rhizosphaera Needle cast which is a fungal problem that affects blue spruce - the Colorado blue spruce in particular. While there are fungicide sprays that can be used to prevent the spread of the problem on a tree, it is not usually recommended to spray unless the problem has actually been diagnosed as present. Different problems can have similar symptoms. Good information on blue spruce and needle cast can be found at:
and also Penn State Extension: http://extension.psu.edu/pests/ipm/agriculture/christmas-tree/pest-fact-sheets/needle-discoloration-...