Rhizosphaera Needle Cast – Colorado Blue Spruce Disease
One of the most common trees planted in the landscapes of Jackson Hole is the Colorado Blue Spruce. Many landowners within Jackson are seeing “holes” appear within their Colorado Blue Spruce trees. The tree looks as though it is hollow, with the interior needles turning color and falling to the ground, leaving only the tips of the branches with needles. With an accumulation of fallen needles surrounding the base of the tree, the tree appears as if it is dying from the inside out. While the fungal disease that is infecting the tree does not cause tree mortality, the holes that are created within the tree cause the tree to lose its aesthetic appeal.
The cause of the needle loss is a fungus called Rhizosphaera Needle Cast. It is one of the most common diseases in blue spruce, and is the result of high moisture levels and poor air circulation which provide a habitat for fungal spores to germinate. Infection of new needles occurs in the spring when spores are released from the fruiting bodies of infected needles. These spores splash or drift onto uninfected needles where, under favorable conditions, they germinate and grow into the needles through their many stomates.
Blue Spruce Tree With Needle Cast
The extent of infection varies, depending on environmental factors that favor the spread of the spores, susceptibility of the tree, stress and years of infection. In situations that we have reviewed in the Jackson Hole area, landscape irrigation combined with sod or other dense types of vegetation growing under or close to the branches of the spruce will lead to high levels of moisture and humidity within the tree. This leads to an environment favorable to the fungal disease.
Treatment typically includes the use of the preventative fungicide chlorothalonil. Alteration of the environment in which the spruce is growing can further mitigate the advance of the disease.
An expert tree evaluation from an ISA Certified Arborist at TLC is available to help you address the health of your trees. For more information or for specific questions about your trees, ask the tree experts at TLC.