Illinois Plant Clinic | St. Louis Public Radio

Illinois Plant Clinic

Trees killed by sudden oak death on a hillside in Big Sur, California, in 2006. The pathogen that causes sudden oak death was found on some ornamental plants in Illinois.
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Updated at 12:45 p.m. Friday to add that the pathogen has been found in Missouri, as well.

A pathogen that’s deadly to some native trees has been found in 10 Illinois counties, including St. Clair and Monroe.

Agricultural officials found Phytophthora ramorum, which causes sudden oak death, on some ornamental plants from big-box garden centers around the state. The pathogen causes dark brown spots on the leaves and branch tips of rhododendron, azalia and lilac, but it is deadly for oaks and certain other tree species.