Seeing dark spots and blighted tissue on our native maple leaves?
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We are seeing leaf spot and leaf blight on several native species, including silver maple (Acer saccharinum), red maple (Acer rubrum), red x silver hybrids (Acer x freemanni) and sugar maples (Acer saccharum) and amur maple (Acer ginnala).
This is maple anthracnose and it is caused by several fungi including Aureobasidium apocryptum, Discula campestris (Gloeosporium), Discula umbrinella and Colletotrichum spp. We have submitted multiple samples to the lab to determine which fungi are bothering our beloved maples.
The unusually cold spring prolonged leaf emergence and the near constant wet conditions were perfect for supporting several fungal and bacterial diseases on plants this year. Maple anthracnose (above photo: Melissa Huntley) has been detected all across Ontario and in several NE United States. We can find it both in the landscape and in the nursery.
The second flush of leaves coming on should hide a lot of these symptomatic leaves. There is no need for management of this disease as infected leaves are usually (mostly) retained on the tree. Keep root system soils aerated and provide supplemental watering when conditions become more consistently hot and dry.
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