Asked June 11, 2020, 4:11 PM EDT

I am the gardener for the city of Riverview and I also take care of my subdivision park. About 8 years ago we planted 6 burgundy wine Nine Bark. They have done well up until this year. They have a lot of die-off on them and 3 of them have a white powdery appearance on some of the leaves, but it doesn't look the same as a powdery mildew on lilacs. Any idea what I should do or do you think it will go away. The majority of the bush looks okay

Wayne County Michigan

5 Responses

Powdery mildew is a common affliction of some ninebark. Some cultivars are resistant and others are highly susceptible. I wasn't able to find information for your particular cultivar. Powdery mildew is really a description of symptoms, a powdery white substance on the surface of the leaves, and is caused by a variety of fungi and fungi-like organisms on different plants. This means powdery mildew on ninebark may appear different on ninebark than on a lilac. Do you have a photo of the ninebark symptoms? That would be helpful with identification. Occasionally dusty substances masquerade as powdery mildew on leaves. That doesn't explain the dieback. I'm not finding any information connecting powdery mildew on ninebark to dieback. If the powdery substance on the leaves is powdery mildew we may need to consider other causes of the die-back including environmental.

Like I said, all 6 seemed healthy up until this spring. They all have it to some degree

Thanks for the pictures. The images are consistent with powdery mildew whether or not that is leading to the dieback. Powdery mildew thrives in high humidity conditions. As the plants have matured do they still have sufficient room for air circulation between the plants? Have you been pruning out older branches?

They are stand alone bushes and get full sun. I have others throughout the city of Riverview but only the burgandy wine were effected. But I probably wasn’t as good as I should have been about pruning the old branches. I cut some of the mildewed branches (not all) and sprayed with a fungicide.

Some cultivars of ninebark are more susceptible than others to powdery mildew. This one could simply be one of the more susceptible cultivars.