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Extension > Garden > Yard and Garden > Trees and shrubs > Brown spot needle blight

Brown spot needle blight

Rebecca Koetter and Michelle Grabowski

MN Dept. of Natural Resources Archive. Bugwood.org

Young pine infected with brown spot needle blight.

Importance

Brown spot needle blight causes needle spots, browning and early needle drop. Infected trees have slow growth and often bare lower branches. Disease can eventually kill young trees that have been infected year after year.

Pathogen and susceptible plants

Brown spot needle blight is caused by the fungus Mycosphaerella dearnessii (syn. Scirrhia acicola). This disease severely affects ponderosa (Pinus ponderosa) and Scots pine (P. sylvestris) in the Great Lakes regions. All pine species in Minnesota are susceptible to some degree, including jack pine (P. banksiana), mugo pine (P. mugo), Austrian pine (P. nigra), eastern white pine (P. strobus), and red pine (P. resinosa) but the disease is not commonly found on these species.

Identification

Biology

E. Barnard, FLDACS, Bugwood.org

Spots and bands caused by brown spot needle blight.

The brown spot needle blight fungus overwinters in diseased needles on the tree or needles that have fallen from the infected tree. In spring, spores are released and spread to new needles by way of rain splash, wind or on contaminated pruning tools. The majority of needle infections occur in spring and symptoms appear several months later. New, succulent growth is most susceptible and is the quickest to show symptoms but all ages of needles can become infected. The needles must be wet in order to be infected by these fungal spores. Once the disease is in an area, annual infections occur as long as weather conditions are favorable.

Management

Always completely read and follow all instructions on the fungicide label.

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