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.
We apologize but do not carry any fungicides labeled for use in hydro see applications.