Rhizosphaera Needle Cast of Spruce Rhizosphaera Needle Cast of Spruce Colorado Blue Spruce is usually a healthy, pest resistant landscape evergreen for eastern Nebraska. This fungal disease affects the lower parts of the tree first, then spreads upward.
Infected needles turn a purplish-brown color and are prematurely cast.
Infection of the tree's needles takes place in the spring, but the tree does not begin to show disease symptoms until the following spring- a year later. At that time, very small black specks begin to appear on the upper surface of the needles. These specks, which can be seen with a hand lens, are fungal spores growing out of the natural openings in the needles called stomata. These fungal spores will go on to infect more needles on the tree. Infected needles usually turn a purplish-brown color, then fall off in late summer of their second growing season, although some needles adhere to the tree branches over winter and produce spores the following spring.