A fungus-like organism known to kill oak trees has made its way to the Midwest, and Minnesota officials are warning residents to be on the lookout for symptoms of the disease.

The invasive plant pathogen Phytophthora ramorum causes sudden oak death disease, according to a news release from the Minnesota Department of Agriculture. In California and Oregon, the pathogen is responsible for killing an estimated 30 to 45 million oak trees. The microorganism also infects over 100 other plants, including rhododendrons.

Several midwestern states have discovered rhododendron shrubs infected with Phytophthora ramorum at retail nursery sites, according to the news release.

Although no infected plants have been found in Minnesota, the state ag department is asking anyone who purchased a rhododendron in 2019 to inspect the plant for symptoms of infection and to report any concerns.

In rhododendrons, infected leaves have large, brown blotches, according to the news release. Young green stems and shoots turn brown and shrivel. Leaves attached to infected stems wilt and may have a dark brown line extending down the center of the leaf from the base. Phytophthora ramorum often does not kill rhododendrons.

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If symptoms are found on new rhododendrons, photos or a description of the symptoms should be reported to the Minnesota Department of Agriculture’s Arrest The Pest line at arrest.the.pest@state.mn.us or 888-545-6684.