The leaves of two Ninebar... - Ask Extension
The leaves of two Ninebark Coppertina shrubs have become covered with a white powder. It has led to the leaves eventually turning black and drying u...
Knowledgebase
The leaves of two Ninebar... #260508
Asked July 09, 2015, 12:39 PM EDT
The leaves of two Ninebark Coppertina shrubs have become covered with a white powder. It has led to the leaves eventually turning black and drying up. I'm guessing a fungus.
What do you suggest for treatment?
Washington County Minnesota
Expert Response
The white powder is a fungus called powdery mildew. It is typically cosmetic and non-fatal to the plants. There are also plants that are more susceptible (and resistant) to powdery mildew. Some Ninebark cultivars are reported to be less susceptible to powdery mildew, but weather conditions can make cause even resistant cultivars to be affected. Here is an Extension publication: http://www.extension.umn.edu/garden/yard-garden/trees-shrubs/powdery-mildew/
Powdery mildew spores are in our environment, so 100% prevention is difficult to impossible. However, pPlanting your shrub in the proper conditions and properly spaced for good air circulation can decrease the severity of powdery mildew. Also proper pruning to open up the canopy and allow air and light to reach the branches can be beneficial.
You may have other issues / pests happening simultaneously that is actually killing the leaves. To treat the issue properly, you can send a plant sample to the U of M Plant Disease Clinic at http://pdc.umn.edu
Powdery mildew spores are in our environment, so 100% prevention is difficult to impossible. However, pPlanting your shrub in the proper conditions and properly spaced for good air circulation can decrease the severity of powdery mildew. Also proper pruning to open up the canopy and allow air and light to reach the branches can be beneficial.
You may have other issues / pests happening simultaneously that is actually killing the leaves. To treat the issue properly, you can send a plant sample to the U of M Plant Disease Clinic at http://pdc.umn.edu
