Powdery Mildew on Pine Bark bush

Asked October 21, 2019, 11:13 AM EDT

I plan to dig out my pine bark bush that is infected with powdery mildew. How do I protect another bush that I hope to plant in that same spot? How do I stop the spread to my other bushes? Are there mildew spores in the soil? Do I need to sterilize the soil? And if so, what do you recommend?
Thank you for your help.
Phyllis

Union County Oregon forestry horticulture

1 Response

Do you mean ninebark? Regardless of the actual plant powdery mildews are plant specific, meaning that a powdery mildew fungus on a cucumber will not affect a rose (or a ninebark). Because the fungus is plant specific, choose a plant that is either not related to the ninebark or choose a variety that is resistant to powdery mildew. Ensure there is adequate spacing to allow air flow between and through the plants. Good pruning techniques will help to mitigate any higher humidity that might be in the planting area and therefore limit potential spread of the fungus.

Cultural, biological, and chemical control can all help to control the disease. Fungicides can be effective but no one fungicide is effective on all powdery mildew so if you choose to use a fungicide be sure your plant is listed on the label and follow all directions as written.

Powdery mildew does not live in the soil so no soil sterilization is necessary. You will, though, need to make sure you completely clean up any plant debris when you remove your plant. Do not compost the plant or debris. Dispose of it in the garbage.

I am including a link to ‘Powdery Mildew Diseases’, an article in the PNW Disease Management Handbook which goes into great detail about the disease, management, and control.

https://pnwhandbooks.org/plantdisease/pathogen-articles/common/fungi/powdery-mildew-diseases