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Black Hills Spruce Diseases

The Black Hills spruce (Picea glauca) is a variety of white spruce native to South Dakota. The Black Hills spruce is a large tree, with one specimen in North Dakota that stands at a height of 95 feet with a 42 foot spread. Generally grown as an ornamental tree, the Black Hills spruce also serves as a windbreak or privacy screen in some residential landscapes. The Black Hills spruce tree grows best in moist, loamy soil in full sun in its USDA hardiness zones (2 to 6).

Lirula Needle Blight

A fungal disease, lirula needle blight overwinters on the tree’s needles and becomes progressively worse over the course of three years. This disease first occurs in the tree’s second year, in late summer. The needles turn brown and appear dead. Apply a fungicide containing chlorothalonil when new needles are half the length of mature needles, and a second time, one month later, according to package directions. This procedure will need to be repeated for every spring for three years to be effective, according to the University of Minnesota Extension Service.

Rhizosphaera Needle Cast

Rhozosphaera needle cast strikes in mid to late summer. It can be identified by yellowing needles that burn brown in late winter. Rhozosphaera needle cast affects the needles on lower branches that are closer to the trunk, rather than those at the tips of the branches. The needles will fall off the tree one year after it is infected. To avoid this disease water the tree during periods of drought, mulch around the base and avoid getting water on the needles. Spray the infected Black Hills spruce tree with a fungicide containing Chlorothalonil, according to package directions, in early spring when new needles are small. Apply again three weeks later, according to package directions.

Cytospora Canker

Another fungal disease that is destructive to the Black Hills spruce. It is introduced into the tree through wounds, starts on the lower branches and spreads quickly to others. Needles turn brown and die and the tree secretes white or light blue resin from lesions on the bark, called cankers. It is primarily spread by rain, insects and birds. Stressed trees, such as those in drought conditions, are more susceptible to the disease, according University of Nebraska-Lincoln. It is, therefore, advised that you keep the tree healthy with proper watering and other maintenance procedures. Early management includes pruning off and destroying diseased branches. After pruning, apply a fungicide to the wounds.

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