No, Daconil Zn Flowable Fungicide cannot be used on blue spruce trees.
We would recommend using Clearys Spectro 90 WDG for needlecast on blue spruce trees. The mixing ratio is 1-2 tablespoons per gallon of water.
Daconil Zn Flowable Fungicide is labeled for commercial treatments on Douglas Firs for Swiss Needlecast. This product should not be applied on residential lawns.