Blue Spruce Needle Cast
Thank you for the question. Unless you have already done so, please confirm that your blue spruce have been accurately diagnosed with a needle cast disease. Other non disease factors and pests can cause browning and death of older needles along with normal age related shedding. The rhizosphaera fungus must be identified before treatment is initiated. For a small fee you can send a sample to the University of Minnesota plant disease diagnostic clinic.
This fungus is spread through splashing water spring through fall, so other trees may be susceptible, especially if they are stressed from poor cultural conditions, other pests, or drought. If the fungus is identified, the trees may be saved by improving watering practices, making sure there is enough space between them to promote good airflow, and spraying with the fungicide chlorothalonil among other measures. Please read the two links provided below to learn more:
Thank you for contacting Extension.