Rhizosphaera needle cast may be the culprit here - it is a common fungus that attacks spruce trees.  However, other fungi result in symptoms very similar to Rhizosphaera, so before you use any fungicide, it's best to send a lab sample to the U of Mn Plant Disease Clinic (https://pdc.umn.edu/) to confirm that Rhizosphaera is responsible for the damage.  For information on this fungus, including how to treat it, see

https://extension.umn.edu/plant-diseases/rhizosphaera-needle-cast

Properly-applied fungicides should be effective.  Take caution when applying any insecticide or fungicide. .  Protect yourself and make sure that no spray falls on you.  This link talks about how to apply these products safely - http://npic.orst.edu/health/safeuse.html