Rhododendron - Ask Extension
Browning leaves followed by death of entire branch started with one of my rhodies. I at first thought it was a problem with lace bugs - but now I do...
Knowledgebase
Rhododendron #878921
Asked July 26, 2024, 2:27 PM EDT
Browning leaves followed by death of entire branch started with one of my rhodies. I at first thought it was a problem with lace bugs - but now I doubt it. I used a root application but stopped because of potential harm to bees. I removed dead branches and now the once healthy branches are dying. This has spread to two other rhododentrons. These are not new plants. They have been in the ground for more than 20 years and perfectly healthy until now. I have made no changes to their care. Can you offer advise? I can bring in a branch to the Yamhill Country extension service if that will help diagnose the issue. I've attached two photos from two different rhodies.
Yamhill County Oregon
Expert Response
Hi Kathi,
I think it would be best to take a couple of the affected branches into the Yamhill County Extension office. Seeing physical specimens is best for disease diagnosis. Plus they will be able to obtain a full and complete history of the damage.
Here is what I observe from the photos. The damage to the two plants in the photos appears maybe sun related? Is the damage around the entire plant or is it centered on one side, like the south side? Were any trees or large shrubs removed in your landscape this past year? Was Casoron used on your landscape. This type of damage may occur on those leaves and leaf parts which orient toward the afternoon sun when Casoron is used.
It might be Rhododendron Leaf Spot, which is a fungal disease.
But these are simply possibilities, by far your best course is to head to the Extension office. Keep in mind that the office is closed or has limited hours this coming week because of the County Fair.
I think it would be best to take a couple of the affected branches into the Yamhill County Extension office. Seeing physical specimens is best for disease diagnosis. Plus they will be able to obtain a full and complete history of the damage.
Here is what I observe from the photos. The damage to the two plants in the photos appears maybe sun related? Is the damage around the entire plant or is it centered on one side, like the south side? Were any trees or large shrubs removed in your landscape this past year? Was Casoron used on your landscape. This type of damage may occur on those leaves and leaf parts which orient toward the afternoon sun when Casoron is used.
It might be Rhododendron Leaf Spot, which is a fungal disease.
But these are simply possibilities, by far your best course is to head to the Extension office. Keep in mind that the office is closed or has limited hours this coming week because of the County Fair.
