The disease pathogen, Phytophthora ramorum, was found in Illinois in 2019. The pathogen was found in some rhododendrons and lilacs that were sold at certain retail outlets. The Illinois Department of Agriculture issued a press release in early July 2019 about the affected plants and the stores through which they were sold. This pathogen causes a blight, known as ramorum blight, on rhododendrons, azaleas, viburnum and lilacs, as well as other plants. Symptoms include leaf discoloration and branch dieback. This blight is generally not fatal to these plants, but they can be carriers of the pathogen. When this pathogen infects oaks, they contract a disease called sudden oak death, which can be fatal. At this time, no oaks in Illinois are known to be infected.
P. ramorum is soil-borne and water-borne and can be spread by infected plant material, soil and water. The University of Illinois Plant Clinic has released more complete information on this disease. Ask the following questions if a plant appears suspect:
Was the plant purchased in 2019?
Is the plant a lilac, rhododendron, or azalea?
Is the plant displaying any of the following symptoms?:
Dark brown spots, blotches, or tip dieback on leaves
Dark brown discoloration along the leaf margin
Dark brown discoloration of the branches, usually starting at the tip of the branch
If the answer to all of the above questions is YES, please contact the Illinois Department of Agriculture at (815) 787-5476.
Here are some important points to remember:
- Sudden Oak Death has NOT been found in Illinois.
- Plants purchased prior to 2019 are unlikely to be infected.
- Plants that are suspected of having this disease should NOT be moved or destroyed. The Illinois Department of Agriculture needs to be contacted.
- Do NOT submit samples to any public garden, plant clinic, park district or U of I Extension office. Contact the Illinois Department of Agriculture. They are the organization that handles this problem.