The Kansas Department of Agriculture’s plant protection and weed control program this week confirmed the presence of a plant disease in hundreds of rhododendrons sold at large retail stores in Kansas. Sudden Oak Death (SOD) is a plant disease that has killed large tracts of oaks and other native species in California and Oregon, and infected rhododendrons have been identified in 10 states in the Midwest, including Kansas. The infected plants that have been found in the Midwest have all been traced back to a common source.
The causal agent of SOD, Phytophthora ramorum, has been detected in rhododendrons originating from Park Hill Plants nursery in Oklahoma, and plants from that nursery were shipped to 60 Walmart stores across Kansas and one Home Depot store in Pittsburg, Kansas. Those stores have cooperated with KDA, USDA, and other states’ plant regulatory staff as they work to destroy all infected and potentially-infected rhododendrons still for sale, along with any other host plants in the vicinity. There is no treatment for the pathogen or disease and infected plants should be destroyed to prevent spread.
Consumers who purchased rhododendrons and other known P. ramorum hosts in April, May or June of 2019 in varieties that have been determined to be infected should take action to dispose of the plants immediately to prevent further spread of the disease. Plants can be destroyed by burning on site, deep burial, or by double bagging in heavy duty trash bags (including the root ball) and disposing into a sanitary landfill where permitted. Varieties that should be destroyed include: Cat Cunningham Blush, Firestorm, Holden, Nova Zembla, Percy Wiseman, Roseum Elegans, and Wojnars Purple.
Other varieties of rhododendrons and other plant species may be infected as well. There are over 100 known species susceptible to P. ramorum, including, trees, shrubs and herbaceous plants. Symptoms of SOD include foliar leaf spots, browning and wilting of leaves, and brown to black discoloration on stems and/or trunks. If you observe symptoms, or are uncertain of the variety of your rhododendron. please contact your local K-State Research and Extension office for assistance.
Sudden Oak Death has not shown to be a health risk to humans or animals, even if nuts, fruit, leaves or berries from an infected plant are eaten.
For photos of symptomatic plants, a list of extension offices, or other information about what you can do to help stop the spread of this plant disease, go to agriculture.ks.gov/SOD. For additional information about SOD, see www.suddenoakdeath.org.