Sawadaea bicornis on bigleaf maple? - Ask Extension
In the past couple of years, I have noticed more and more bigleaf maples in my area infected with Sawadaea bicornis mildew. I've read a few st...
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Sawadaea bicornis on bigleaf maple? #875876
Asked July 03, 2024, 6:52 PM EDT
In the past couple of years, I have noticed more and more bigleaf maples in my area infected with Sawadaea bicornis mildew. I've read a few studies that indicate that this mildew may be partially responsible for bigleaf maple decline in Washington. Is there any group tracking the spread of this disease in Oregon? I've includes some pictures from local trees.
Clackamas County Oregon
Expert Response
Powdery mildew is common and widespread in bigleaf maple these days, particularly when we get more rain in late spring/early summer. While chronic leaf disease year after year can increase a tree's vulnerability to other stressors, powdery mildew is still not generally considered a major health threat.
Powdery mildew does not seem to be a major factor in bigleaf maple dieback. The major agents implicated in the more serious maple dieback cases are climate stress, human development impacts, and leafhopper insects.
See references:
https://www.oregon.gov/odf/Documents/forestbenefits/tree-declines-bigleaf-maple.pdf
https://botanicgardens.uw.edu/wp-content/uploads/sites/7/2022/03/WA_Botanical_Symposium_Betzen_BigleafMapleDecline.pdf
https://pnwhandbooks.org/plantdisease/host-disease/maple-acer-spp-powdery-mildew
Powdery mildew does not seem to be a major factor in bigleaf maple dieback. The major agents implicated in the more serious maple dieback cases are climate stress, human development impacts, and leafhopper insects.
See references:
https://www.oregon.gov/odf/Documents/forestbenefits/tree-declines-bigleaf-maple.pdf
https://botanicgardens.uw.edu/wp-content/uploads/sites/7/2022/03/WA_Botanical_Symposium_Betzen_BigleafMapleDecline.pdf
https://pnwhandbooks.org/plantdisease/host-disease/maple-acer-spp-powdery-mildew
