Yellowing Phlox Leaves - Ask Extension
I’m starting to see yellowing on the leaves of two neighboring Phlox ‘cloudburst’ plants. I have others in another bed with no issues. I’m...
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Yellowing Phlox Leaves #793812
Asked June 02, 2022, 10:49 AM EDT
I’m starting to see yellowing on the leaves of two neighboring Phlox ‘cloudburst’ plants. I have others in another bed with no issues. I’m used to seeing small circular damage from 4-line bugs but I haven’t seen leaf damage like this so shortly after leafing out this early in the season. Any reason for concern?
Washtenaw County Michigan
Expert Response
I tried to upload a picture, which I've done with ease in the past, but I was unable to both on my phone and my laptop. The original pictures were from my Iphone in HEIC format which by default may have been too large. I converted to them to JPEG and reduced the size but still couldn't upload them.
Yellowing Phlox photos
another yellowing phlox photo
Good Morning,
I suspect Leaf spot and/or Blight. Leaf spot causes a litter of dots to appear on affected leaves, typically consisting of a mix of yellows and browns. Numerous types of fungi cause the disease, but all of them thrive in humid conditions. Taking the same preventive approach as powdery mildew, by watering the plant early in the day, often keeps humidity levels manageable. Phlox plants that are overcrowded may also suffer from high humidity levels. Botrytis blight causes leaves to yellow, either partially or completely. Flower buds appear discolored, die or may not open at all. Leaves eventually turn black and stems typically die. Allowing for good air circulation -- by ensuring your phlox plants have plenty of room -- and keeping humidity down prevents the disease from occurring. For both leaf spot and blight, remove fallen plant material immediately and cut away dead material. You could submit a sample for a small fee to get a firm diagnosis.
Plant & Pest Diagnostics (msu.edu)
References
Verticillium wilt of Perennials - Plant & Pest Diagnostics (msu.edu)
Problems Causing Phlox to Turn Yellow (sfgate.com)
Problems Causing Phlox to Turn Yellow (sfgate.com)
I hope this helps. Thanks for using our service.
I suspect Leaf spot and/or Blight. Leaf spot causes a litter of dots to appear on affected leaves, typically consisting of a mix of yellows and browns. Numerous types of fungi cause the disease, but all of them thrive in humid conditions. Taking the same preventive approach as powdery mildew, by watering the plant early in the day, often keeps humidity levels manageable. Phlox plants that are overcrowded may also suffer from high humidity levels. Botrytis blight causes leaves to yellow, either partially or completely. Flower buds appear discolored, die or may not open at all. Leaves eventually turn black and stems typically die. Allowing for good air circulation -- by ensuring your phlox plants have plenty of room -- and keeping humidity down prevents the disease from occurring. For both leaf spot and blight, remove fallen plant material immediately and cut away dead material. You could submit a sample for a small fee to get a firm diagnosis.
Plant & Pest Diagnostics (msu.edu)
References
Verticillium wilt of Perennials - Plant & Pest Diagnostics (msu.edu)
Problems Causing Phlox to Turn Yellow (sfgate.com)
Problems Causing Phlox to Turn Yellow (sfgate.com)
I hope this helps. Thanks for using our service.
