Maple leaf spot
Damage, symptoms and biology
The fungus creates small brown spots on the leaves and, in severe infections, when most of the foliage is affected, the leaves may be shed prematurely. Growing leaves are infected in the spring and initially develop yellowish-green spots. The leaves eventually die and turn a brownish colour. Black fruiting bodies of the fungus develop in the infected spots around the end of autumn. The spores produced by these fruiting bodies over winter in the leaf litter and cause new infections the following spring.
As with many foliar fungal diseases, cool, wet spring weather greatly favours the spread of the disease. To protect ornamental trees, the leaves of affected trees should be carefully collected and destroyed by burning or composting.
Canadian Forest Service Publications
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