Miniature Alberta Spruce Diseases

Rhizosphaera Needle Cast

• Rhizosphaera needle cast disease is brought on by the fungus Rhizosphaera kalkhoffii and causes the needles of the miniature Alberta spruce to take on a spotted, yellow or reddish-brown appearance. Much later -- often a year or more -- the needles turn a purplish-brown color and fall from the tree. The first symptoms of needle cast disease typically display in the spring on the lower branches before spreading up and around the spruce.

Needle Cast Management

• As needles fall from the dwarf Alberta spruce, entire branches may die but needle cast disease rarely kills an entire tree unless the condition persists for several successive years. Infection occurs during warm, wet weather and diseased branches, needles and other litter should be pruned away or removed from the ground to help prevent spread of the disease. Good air circulation should be encouraged around the tree and copper-based fungicides are effective in managing Rhizosphaera needle cast.

Lirula Needle Blight

• The fungus Lirula macrospora causes Lirula needle blight, a condition where second-year needles become discolored with a yellow or brown tint. The fungus overwinters on affected foliage before coming to life in the spring with needles on lower branches being infected first and younger needles the most susceptible. A raised black line which is a fungal reproduction center forms on second year needles. The disease then forces the needles to turn a grayish-brown color although they can remain on the tree for several years.

Spruce Needle Rust

• Spruce needle rust caused by fungi of the genus Chrysomyxa turns needles at the tips of branches yellow. Light orange or white tube-like structures jut out from diseased needles in summer and release a powdery, orange fungal spore. The tree may take on a tan or pink tinge with infected needles falling away in early fall. Spruce needle rust is primarily an aesthetic problem, but its impact can be reduced by allowing for good air circulation around the specimen.