Picture from a survey by the Department of Natural Resources shows a rhododendron with sudden oak death, a dangerous disease that could kill Indiana's oak trees if it's not contained. (Photo: Department of Natural Resources)
As reported in the Brown County Democrat: http://www.bcdemocrat.com/2019/05/30/sudden-oak-death-pathogen-found-in-plants-sold-at-walmart-rural-king
More than 70 Walmart stores and 18 Rural King stores in the state have received rhododendron plants infected with sudden oak death (SOD), a fungal pathogen that kills oak trees. Shipments containing infested material were sent to nine other states as well.
SOD can kill standing oak trees, which could happen if SOD-positive rhododendron were planted within about 6 feet of a standing oak.
Inspectors from the DNR Division of Entomology & Plant Pathology initially detected SOD (Phytophthora ramorum) in several varieties of rhododendrons being sold in Columbus, Noblesville, South Bend, Sullivan and Tippecanoe.
Inspectors have been visiting stores in other communities across Indiana to destroy any stock that has been found infested and quarantine any stock that is symptomatic. The division has made this its top priority, according to a press release from the Indiana Department of Natural Resources.
The DNR has destroyed about 1,500 infested rhododendron so far and pulled another 1,500 from stores. The DNR has also ordered these stores to stop selling rhododendrons until further notice. Any quarantined material that is not infected will be released after testing at Purdue University.
SOD has killed large tracts of oaks on the West Coast. SOD has not been established in the Midwest to date.
Many of Brown County’s forests are anchored by oak trees.
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
The DNR is also following up with homeowners who have called in to say they’ve purchased plants they believe are infested or are seeing signs/symptoms of sick trees in the environment.
If you have purchased rhododendrons in the last four weeks from Walmart or Rural King, destroy them, or call 1-866-NO-EXOTIC (663-9684).
Kara Hammes, Brown County Purdue Extension educator for agriculture and natural resources, advises residents to dispose of these plants by doing the following:
- Double-bag plant material, pots and soil for disposal.
- Move potentially infected plants around as little as possible before bagging.
- Plant material can be burned, if burned immediately, and pots and soil-double bagged for disposal.
- Avoid planting other susceptible species in previously planted areas. See https://www.aphis.usda.gov/plant_health/plant_pest_info/pram/downloads/pdf_files/usdaprlist.pdf
For more information, call the Brown County Purdue Extension office at 812-988-5495
More information about the biology and life cycle of the pathogen can also be found on the Purdue Landscape Report: