White fungus on a Japanese maple

Updated February 21, 2017

Nearly all ornamental plants suffer infection from a fungal disease known as powdery mildew. Japanese maple trees are likely to survive an attack, although the disorder can be unsightly with a white, powdery growth coating the plant's otherwise attractive-looking leaves.


A white fungus known as powdery mildew is one of several leaf diseases prone to attacking the brightly coloured Japanese maple tree, Acer palmatum. Japanese maples may also be troubled by anthracnose, leaf spot, leaf scorch, root rot, aphids, scales and borers.

Powdery mildew

Powdery mildew appears as a white or grey fungal substance throughout the leaves, stems, flowers and fruit of a plant. Leaves may curl or twist even before the white fungus is apparent. Severe powdery mildew infection will result in yellowed leaves, dried and brown leaves, and disfigured shoots and flowers.


The disease rarely results in the death of the Japanese maple, but it may increase the likelihood of leaves falling prematurely and the tree moving into autumn dormancy earlier than normal. Trees typically suffer infection when temperatures range between 15C and 27C; powdery mildew normally does not appear during the extreme heat of summer or cold of winter.

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About the Author

Mark Bingaman has entertained and informed listeners as a radio personality and director of programming at stations across the U.S. A recognized expert in the integration of broadcast media with new media, he served as associate editor and director of Internet development for two industry trade publications, "Radio Ink" and "Streaming Magazine." Today, he heads the International Social Media Chamber of Commerce.