Powdery mildew on Crimson King Maple

Discussion in 'Outdoor Gardening in the Pacific Northwest' started by Curious Arborist, Jun 22, 2010.

  1. Curious Arborist

    Curious Arborist Member

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    How can I get rid of what appears to be powdery mildew on the leaves of my Crimson King maple. This mildew appears every year at this time. The tree was pollarded 3-4 years ago. Since then it has been selectively pruned in an attempt to perform a structural crown restoration. Any suggestions?
     
  2. ryansenechal

    ryansenechal Active Member

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    Pollarding is not a single event, but an annual technique starting with a young tree. Single event heavy reductions fall under two categories -- one being topping and the other being a crown reduction (which is usually a response to a declining tree dying from the crown tips inward). Proper pollarding puts enormous stress on a tree which can weaken defense to common pathogens and insects. Topping and crown reductions have a more drastic effect, amplified by large wounding.

    Now for your Powdery Mildew issues:
    Port Coquitlam's municipal cosmetic fungicide ban takes all chemical controls off of the table. Crimson King is naturally very susceptible to the pathogen and although the issue catches your eye, it likely is not much more than a cosmetic issue. Leaf wetness is the primary factor after this very wet, cool spring.
     
  3. Ron B

    Ron B Esteemed Contributor 10 Years of Activity

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    I'd say the mildew in this case is probably a byproduct of the pruning*, the one that really mildews too much down here - whether pruned or not - is the 'Crimson King' bud sport Crimson SentryTM. Since both are examples of Acer platanoides I would not grow either. This region does not so far have the Norway maple problem of eastern North America but there are places in and near Seattle where appalling numbers of the things have popped up - despite our dry summer conditions. In fact, these seedlings appear to be more drought resistant and much better at persisting through the first year than our native A. macrophyllum.

    *Unless these are pretty much now all mildewing up there, perhaps with a different strain of mildew present than we have here
     
  4. ryansenechal

    ryansenechal Active Member

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    Likewise.
     
  5. Michael F

    Michael F Esteemed Contributor Forums Moderator 10 Years of Activity

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    Agree, best to get rid of it, given its invasive habits.

    For clarification, not necessarily (nor usually) annual; pollarding rotations are typically anything from 3-20 years.
     

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