Needlecast is a very common, yet deadly, disease that affects spruce trees throughout the region. It is easily identified as it thins spruce trees out from the middle, leaving only very little growth, if any, just at the ends of the branches. It generally starts near the bottom of the trees and slowly works its way up, killing off branches as it continues. Infected needles turn purple, then brown, before ultimately falling (or casting) from the tree. If left untreated, this disease can ultimately kill spruce trees.
Being a fungus, needlecast thrives in cool, damp locations. This is why it attacks the inside of the tree first, where airflow is minimal. Excessive water can also contribute to the spread of the disease, which is why it is important, if the area is irrigated, to make sure the surrounding sprinkler heads are adjusted so they do not directly hit the trees.
Unfortunately, there is no fungicide that kills this fungus. What is available for use is a protectant. Properly timed sprays in the Spring and Summer are critical to helping protect the new growth that is emerging from getting infected.
It is important to remember that even after treatments begin, previously infected needles will continue to turn color and fall off the tree. This isn’t a sign that the treatments are not working, it is just that once the needles are infected there is little to no hope of saving them and those infected needles will continue to fall as they die off.
With properly timed annual treatments, it is possible, over time, to restore the tree’s foliage back to the thick, full canopy that spruce trees are known for.