When I worked in a commercial mill they tried to cut and mill all the pine in the winter, this pine never had any blue stain at all. As Diaku mentioned the fungus needs warmth and moisture. If the lumber is stickered and air dried before warm weather it's too dry for the fungus to grow.
Not sure what NP-1 consists of
,but I'd breath easier if I knew any sawdust I'm generating does not contain fungicide
