The blue spruce (Picea pungens) is also known as Colorado blue spruce and silver fir and is native mainly to the western U.P. and the Rocky Mountains. An excellent windbreak tree, the blue spruce is susceptible to fungal diseases that cause drop their needles brown or red and prematurely.
A lack of moisture is the prime suspect when the blue spruce is losing its needles. The first symptom of water stress, the browning of the needles is followed by their release on the ground. In addition to summer drought, a sequence of three dry winters will damage the needles. Additional water should be used in the ground around the blue spruce in the winter months. The tree is not well suited to high heat or dry wind.
Needle Cast Disease
If a blue spruce is red and lose their needles, it is probably in front of a crowd of knit disease caused by the fungus Rhizosphaera kalkhoffii. This disease often awakened to life in moist, warm weather, when the temperature in the range of 65 to 75 degrees Fahrenheit, with the fungal spores spread easily by warm rain. It causes the needles of spruce stain on a reddish-purple, brown or yellow before they fall from the tree.
Needle Cast Management
Black fruiting bodies of the fungus will also form on infected needles. The red color on the needles of the blue spruce typically occur in August, followed by a browning of the needles, and then fall. When the branches are completely defoliated for a period of four to five years, the stress can eventually kill the tree. Fallen needles should be raked up and disposed of. Fungicides are available to combat this disease.
Pine Needle Rust
Spruce needle rust, caused by several species of fungi of the genus Chrysomyxa is so called for showing the red, pink or orange color of the disease on the needles of blue spruce. The disease is initially running as yellowing needles following year near the tips of the legs, through the development of reddish-orange or white projections on the needles. These growths serve as reproductive center of the fungus and let go orange or red spores into the wind.