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Extension > Garden > Yard and Garden > Rhizosphaera needle cast

Rhizosphaera needle cast

Michelle Grabowski - University of Minnesota Extension Educator
Cynthia Ash Kanner - former University of Minnesota Extension Specialist

Back to Diseases of spruce trees in Minnesota

Rhizosphaera

Photo by M. Grabowski

This disease is caused by the fungus Rhizosphaera kalkhoffii and is probably the most common needle disease in Minnesota.

Colorado blue spruce, Picea pungens, is highly susceptible to this disease. White spruce (including Black Hills spruce), P. glauca, is intermediate in susceptibility and Norway spruce, P. abies, is relatively resistant. Trees that are stressed from drought, poor planting practices, or other factors are more likely to suffer from Rhizosphaera needle cast.

Rhizosphaera

Photo by J.Albers MNDNR
Bugwood.org

Identification

Biology

The pathogen overwinters on living and recently killed needles. Spores, called conidia, are dispersed by splashing water spring through early autumn. New needles on the lower branches are most commonly infected but if conditions are very favorable for infection (extended periods of moisture on the needles at 77° F) any needles can become infected.

Rhizosphaera

Photo by M.Ostry USDA FS, Bugwood.org

Management

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