The blue spruce tree (Picea pungens) is a hardy ornamental grown predominantly in the central and western United States. The blue spruce, also called Colorado spruce, is tolerant of temperatures as low as minus 40 degrees Fahrenheit and thrives in a moist environment. Blue spruce is rarely threatened by pests or diseases. The two most common blue spruce diseases are needle cast and cytospora canker.
Things You'll Need
- Pruning shears
- Rubbing alcohol
- Yard bags
Inspect the needles of a blue spruce tree for signs of disease. Needle cast disease is characterized by a discoloration of the needles, followed by premature needle dropping. Cytospora canker symptoms include a browning of affected branches, as well as a sticky white sap-like residue.
Prune back blue spruce to remove diseased branches. Cut 4 to 6 inches below the areas of visible disease, including brown needles and bare branches. Clean the pruning shears with rubbing alcohol before and after pruning to prevent spread of the fungus.
Bag pruned branches and fallen needles and discard with your yard waste. The fungus may have an opportunity to spread if bags are not sealed appropriately.
Give your ailing blue spruce tree room to grow, recover and breathe. Remove leaves and other debris, both organic and synthetic, from under the tree. Avoid planting other bushes, flowers and plants too close to the tree.
Apply a lime- and copper sulfate-based fungicide to spruces suffering from needle cast. Spray the tree when the needles are half-grown and then again once the needles have reached maturity. You may need to apply chemicals every few weeks for up to two years to completely protect your tree from the disease.