Officials: Sudden Oak Death Disease moving towards Minnesota, spreading through flower shrubs

Minnesota Department of Agriculture officials are asking the public to be on the lookout for signs of Sudden Oak Death Disease in plants.

Officials say the disease is responsible for killing more than 30 million oak trees in forests along the West Coast, and has spread to the Midwest through infected rhododendron shrubs.

Rhododendron are among more than 100 plants that can be infected by the fungus-like microorganism that causes the disease, according to officials. Officials say infected plants often will not die but will show symptoms in the form of large, brown blotches on leaves; a dark brown line extending down the base of leaves or young, green stems turning brown and shriveling.

The MDA says no infected plants have been found in Minnesota so far, but are asking people who have purchased Rhododendron plants in 2019 to look for symptoms of the disease.

The MDA asks that owners of infected rhododendrons send photos or a description of the symptoms to the Minnesota Department of Agriculture’s Arrest The Pest line at or 1-888-545-6684.

“While rhododendrons may not die from this plant disease, our main concern is that the plants act as carriers of Phytophthora ramorum and could spread spores to Minnesota’s oaks,” said MDA Plant Pathologist Michelle Grabowski. “Phytophthora ramorum has never been identified in Minnesota but it could have significant impact on the state’s forests and landscapes. Tests have shown that native trees like Northern red oak and white oak can be infected with Phytophthora ramorum.”

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