USDA’s Animal and Plant Health Inspection Service (APHIS) has confirmed that more than 50 rhododendron plants found in Indiana nurseries have tested positive for Phytophthora ramorum (P. ramorum), a water mold pathogen that causes sudden oak death, ramorum leaf blight, and ramorum dieback. The Indiana Department of Natural Resources detected these plants during this year’s national P. ramorum survey, which APHIS coordinates with participating states.
The infected rhododendron plants were part of a larger shipment that originated from nurseries in Washington State and Canada. APHIS is working with officials from those locations to trace the distribution of plants from this shipment, which were sent to 18 states, including Alabama, Arkansas, Iowa, Illinois, Indiana, Kansas, Kentucky, Michigan, Missouri, Nebraska, North Carolina, Ohio, Oklahoma, Pennsylvania, Tennessee, Texas, Virginia, and West Virginia.
Agriculture officials in these states are sampling plants received from the originating nurseries. APHIS has confirmed positive nursery stock in nursery establishments in eight of these states (Iowa, Illinois, Indiana, Kansas, Missouri, Nebraska, Oklahoma, and Washington). Plants that test positive for P. ramorum are being destroyed. All plants that are within a two meter radius of an infected plant are also being destroyed. Host plants outside the two meter radius will be sampled intensively. Several major retailers have agreed to initiate a voluntary recall of plants from their stores. APHIS will continue trace-back operations and will work with cooperators to ensure risk mitigation measures are in place for all positive plants.
Gardeners and homeowners who have recently purchased a rhododendron from a retail outlet in any of the 18 states listed above should monitor the plant for signs of disease, including leaf spots and shoot dieback. Please contact your local state department of agriculture or extension office if you suspect your plant(s) might have the disease.
For more information on this incident or the federal P. ramorum regulatory program, you may contact the National P. ramorum Program Manager, William Wesela, at (301) 851-2229.