- Black-edged red fungi in maple trees may be the condition known as Phyllosticta leaf spot, brought on by the pathogen Phyllosticta minima. The fungus results in circular, tannish spots bordered by a red or purple hue. The combination of these two colors often appears to be a black circle dotting the leaves of a maple.
- Red, silver, Japanese and amur maples are among the trees most significantly affected by Phyllosticta leaf spot. "Although this disease is quite noticeable in the landscape, especially on silver and red maples and causes concern among homeowners, damage is minimal and fungicides are rarely necessary," advises the Ohio State University Extension Service.
- Infestation by the maple bladdergall mite, V. quadripedes, produces a condition called leaf gall as the mites feeds on the leaves of a maple. Penn State University's College of Agricultural Sciences notes that this fungus typically appears in May, resulting in a green ball of fungus that turns red then black.
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