The Missouri Department of Agriculture, in coordination with USDA Animal and Plant Inspection Service, has detected ramorum blight on rhododendron plants shipped to some retail nurseries in Missouri. The disease is more commonly known as Sudden Oak Death when it infects oak trees. The rhododendrons were shipped to Wal-Mart and Rural King stores throughout Missouri, as well as the Springfield Home Depot, Stark Bros. Nursery Garden Center and Fort Leonard Wood PX.
Consumers who purchased rhododendrons or lilac plants of the known infected varieties labeled Park Hill Plants from these stores between March and June of this year should dispose of the plants immediately. Consumers who are unsure of their plant's variety should look for wilting or browning leaves, leaf spots and twig dieback. If consumers notice these symptoms, they should contact the Department’s Plant Pest Control team at 573-751-5505 and begin the disposal process.
Varieties that have been infected should be disposed of immediately to prevent further spread of the disease. Plants may be destroyed by burning, deep burial or by double-bagging the plant with its root ball in heavy duty trash bags for disposal into a sanitary landfill (where allowable). Consumers should not mulch, compost or dispose of the plant material in municipal yard waste. Garden tools used to dig up any affected plants should also be sanitized before they are used again.
Sudden Oak Death is a form of ramorum blight and is caused by a fungus-like pathogen known as Phytophthora ramorum. Since the 1990s, the plant disease has caused mortality in some types of oak trees in California and Oregon, but it has not established itself in the Midwest. The disease has a host list of more than 100 species of trees and shrubs, including rhododendrons.
Since early June, the Department has worked alongside USDA-APHIS to visit more than 113 retail locations to collect samples and place potential host plants under quarantine. USDA-APHIS has worked with Wal-Mart to organize a voluntary recall of the impacted plants, while other locations have isolated or destroyed affected plants. Any remaining plants confirmed with ramorum blight, and any host species comingled with the confirmed positive plants, will be destroyed.
Shipment of these rhododendrons has been successfully traced back to Park Hills Plants in Oklahoma and may have originated from nurseries in Washington State and Canada. Plant varieties identified during the investigation, which is still partially ongoing, were shipped to at least 18 states.
Specific varieties of rhododendrons that have tested positive in destination states include:
Cat Cunningham Blush, Firestorm, Holden, Nova Zembla, Percy Wiseman, Roseum Elegans, and Wojnars Purple.
Specific varieties of lilac that have tested positive in destination states include:
Common Purple and Persian Lime.
To learn more about the Missouri Department of Agriculture or its programs, visit Agriculture.Mo.Gov.