Photinia Black spot - Ask Extension
I have a hedge across the back of my PDX city lot that that is healthy on my side, but the newish neighbors on the other side have not taken care of a...
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Photinia Black spot #875631
Asked July 02, 2024, 11:21 AM EDT
I have a hedge across the back of my PDX city lot that that is healthy on my side, but the newish neighbors on the other side have not taken care of and it now has a lot of damage due to spotting and one plant on the north edge has died. The foliage is pretty thin and spotty for about 1/2 of the length of the hedge. The hedge is about 30 feet tall. I was not aware it was that bad and talked to them and told them I would take over maintenance of that side and they were fine with that.
I have removed the fallen leaves on their side and trimmed back some of the longer branches and want to know what sort of spraying schedule I can use to restore that side of the hedge. I am aware of the fungicide but don't know the schedule I should use, can I start it now and how often? Should the dosage be increased? Should the soil be treated?
In addition, what other pruning, if any should I do? I don't want to remove too much foliage even if it has spots unless that is a recommendation.
Any other advice?
Thanks
Steve
Multnomah County Oregon
Expert Response
Photinia is known to get leaf spot, a fungus, in our area. There is also a leaf spot that occurs some years for unknown reasons, and is not a disease. I’ll share a couple of pages about the treatments. You begin spraying as new leaves emerge, as the material is protective rather than a cure.
Here is the WSU Hortsense page. This is the PNW Handbook page. It includes a link to the physiological leaf spot information. The handbook is geared to commercial clients, and the boxed “H” indicates homeowner chemicals. For a hedge this tall, I recommend hiring a certified arborist for a spray program.
I hope you’ll stick with me and share more photos though. You might not have fungal leaf spot, or that might not be the biggest issue facing your hedge. Share a couple leaf photos, both sides. Tell me about the new fence and retaining wall on neighbors side. Is that all new? Was there trenching or soil removal in the root area of the hedge? Do you know why the end plant died? How does the bark health appear on remaining trees? What direction is the hedge—your side east, theirs west? Are you in area especially hit be cold winds down the gorge in winter? Have trees been removed or pruned which changed the amount of sun on the plants recently?
Generally, heavy pruning or fertilizing of stressed trees isn’t recommended. It’s okay to take a few years to do the corrective pruning.
I look forward to hearing back from you.
Here is the WSU Hortsense page. This is the PNW Handbook page. It includes a link to the physiological leaf spot information. The handbook is geared to commercial clients, and the boxed “H” indicates homeowner chemicals. For a hedge this tall, I recommend hiring a certified arborist for a spray program.
I hope you’ll stick with me and share more photos though. You might not have fungal leaf spot, or that might not be the biggest issue facing your hedge. Share a couple leaf photos, both sides. Tell me about the new fence and retaining wall on neighbors side. Is that all new? Was there trenching or soil removal in the root area of the hedge? Do you know why the end plant died? How does the bark health appear on remaining trees? What direction is the hedge—your side east, theirs west? Are you in area especially hit be cold winds down the gorge in winter? Have trees been removed or pruned which changed the amount of sun on the plants recently?
Generally, heavy pruning or fertilizing of stressed trees isn’t recommended. It’s okay to take a few years to do the corrective pruning.
I look forward to hearing back from you.
