Rhododendron wilt, browning and die - Ask Extension
This started happening in June this year. Both to oak and rhododendrons. I see it every so often and cut it out but this year it's taking over in this...
Knowledgebase
Rhododendron wilt, browning and die #875702
Asked July 02, 2024, 4:20 PM EDT
This started happening in June this year. Both to oak and rhododendrons. I see it every so often and cut it out but this year it's taking over in this area. All of this is native and I don't water or treat any of this area. Do you know what's going on?
Thanks
Curry County Oregon
Expert Response
There are a couple Phytophthora fungal diseases that might be involved here.
The first is Phytophthora root rot - https://pnwhandbooks.org/plantdisease/host-disease/rhododendron-phytophthora-root-rot. Check out the symptoms listed here and compare with what you are seeing on the shrubs.
Ramorum Leaf Blight and Shoot Dieback (caused by Phytophthora ramorum) has been known to be present in Curry County since its discovery in 2001 north of Brookings. It also causes the disease Sudden Oak Death in oak trees - https://pnwhandbooks.org/plantdisease/host-disease/rhododendron-ramorum-leaf-blight-shoot-dieback
The only way to know for sure would be to submit a plant sample to a lab for identification. The Oregon State University Plant Clinic provides this service (for a fee). Here is a link - https://bpp.oregonstate.edu/plant-clinic/submit-sample/services-and-fees. The Oregon Department of Agriculture also provides this identification service (for a fee) - https://www.oregon.gov/oda/programs/PlantHealth/DiagnosticServices/Pages/PlantPestsDiseases.aspx
The first is Phytophthora root rot - https://pnwhandbooks.org/plantdisease/host-disease/rhododendron-phytophthora-root-rot. Check out the symptoms listed here and compare with what you are seeing on the shrubs.
Ramorum Leaf Blight and Shoot Dieback (caused by Phytophthora ramorum) has been known to be present in Curry County since its discovery in 2001 north of Brookings. It also causes the disease Sudden Oak Death in oak trees - https://pnwhandbooks.org/plantdisease/host-disease/rhododendron-ramorum-leaf-blight-shoot-dieback
The only way to know for sure would be to submit a plant sample to a lab for identification. The Oregon State University Plant Clinic provides this service (for a fee). Here is a link - https://bpp.oregonstate.edu/plant-clinic/submit-sample/services-and-fees. The Oregon Department of Agriculture also provides this identification service (for a fee) - https://www.oregon.gov/oda/programs/PlantHealth/DiagnosticServices/Pages/PlantPestsDiseases.aspx
