Sudden Oak Death, a disease that has killed large tracts of oaks and other native species in California and Oregon, has come to Kansas for the first time — via rhododendrons sold at Kansas Walmarts.
The Kansas Department of Agriculture reported confirmed cases of the incurable plant disease on rhododendron plants sold at 60 Walmarts across Kansas and one Home Depot in Pittsburg, Kansas. The infected plants originated from Park Hill Plants nursery in Oklahoma.
Because there is no cure for the disease, all rhododendrons from this grower identified to be hosts or that could become hosts have been destroyed by the area retailers.
Anyone who has bought these plants also should destroy them.
Sudden Oak Death is a tree disease caused by the fungus-like plant pathogen Phytophthora ramorum, according to the KDA. In rhododendrons, camellias and other common horticultural plants, it causes blight.
The disease recently affected large plots of trees and other native plant species in northwestern states of the United States, and also has also been identified in 10 Midwestern states.
The best ways to destroy the plants is to double-bag them in trash bags and throw them away, including the root ball.
Matthew McKernan, Kansas State University extension agent for Sedgwick County, said he recommends double-bagging over burning, which could leave some of the infected material.
Heather Landsdowne, KDA communications director, said the disease can be spread through water runoff and surrounding soil. Once it’s been introduced, it lingers in residual plant tissues.
“That’s really why we released this information, because we want people to destroy the plants that might be infected,” Landsdowne said.
According to the KDA, the following types of rhododendron purchased from the above stores should be destroyed:
▪ Cat Cunningham Blush
▪ Nova Zembla
▪ Percy Wiseman
▪ Roseum Elegans
▪ Wojnars Purple
The above plants may not be the only plants affected. Red oak trees are susceptible. In addition, more than 100 species can be infected by Phytophthora ramorum.
The KDA and United States Department of Agriculture say that any gardening materials, including shoes, that might have been in contact with infected plants must be sanitized.
McKernan said the wet weather isn’t necessarily to blame for the disease’s appearance in Kansas, but increased rainfall does create conditions more susceptible to water mold diseases, which is what Phytophthora ramorum is.
“Because we’ve had a significantly rainy spring, the conditions have been favorable for this disease if it were to be introduced,” McKernan said.
While the disease poses a threat to plants in Kansas, McKernan stressed that there is no risk to humans or animals.
Symptoms of the disease include, but are not limited to “foliar leaf spots, browning and wilting leaves, and brown to black discoloration on stems and/or trunks,” the KDA said.
Observed or “uncertain” symptoms should be reported to the local Kansas State University Research and Extension offices, McKernan said.
“It’s better to be safe than sorry,” McKernan said. “Pulling out a plant that might be infected is less costly in the long run than allowing that disease to establish.”