The Indiana DNR confirmed that it has intercepted plants containing a fungal pathogen that kills oak trees, sudden oak death (SOD), for the first time in about 10 years.
Inspectors from the DNR Division of Entomology & Plant Pathology detected SOD (Phytophthora ramorum) in several varieties of rhododendrons being sold in Columbus, Noblesville, South Bend, Sullivan and Tippecanoe.
SOD has killed large tracts of oaks on the West Coast. SOD has not been established in the Midwest, to date. SOD can kill standing oak trees, which could happen if SOD-positive rhododendrons were planted within about 6 feet of a standing oak.
SOD travels in more than a hundred species of host plant material. It causes some browning of the leaves in the host but does not kill it. For a list of those plants see the following https://www.aphis.usda.gov/plant_health/plant_pest_info/pram/downloads/pdf_files/usdaprlist.pdf
If you have purchased rhododendrons in the last four weeks in these communities, call 1-866-NO-EXOTIC (663-9684) or call the local county extension office at 1-888-EXT-INFO (1-888-398-4636) for instructions.
The DNR is destroying all rhododendrons from the source nursery, Park Hill Plants (Oklahoma), and any other host plants that were co-mingled with them. In addition, the DNR is quarantining the sale of four other common SOD host plants (viburnum, azalea, cameilia, and pieris) for further testing to determine if they contain SOD. Testing will determine if other species are infested and require destruction.
This is an ongoing investigation, and guidance could change as more information is gathered.