“Why are the leaves on my (maple, sycamore, birch, catalpa, ash, basswood, tuliptree, walnut, hickory, horse chestnut, London planetree) turning brown?!”
Most likely, it’s Anthracnose.
It’s a fungi disease that’s widespread among hardwoods in the Eastern US. Anthracnose spreads via spores, which in turn are spread about by wind and rain. So, when Spring is wet and cool with long rainy periods, the disease will be quite evident.
The symptoms of Anthracnose vary, but will exhibit as blotches or dead areas on leaves, ranging from tiny dead spots to large dead blotches with leaves falling prematurely (see image below). Also look for twig, bud and fruit damage which can cause cankers, thereby killing branches.
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| Anthracnose-affected maple leaves |
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The fungi which cause Anthracnose overwinters on infected debris. During rainy springs, microscopic spores are windblown or splashed onto host trees. The spores germinate, and the fungi begin penetrating new leaves. Summer spore infection can also occur on some tree species.
What to do?
For residential trees, there are several options:
For residential trees, there are several options:
- Pruning is important, as this allows better air movement and sunshine into the canopy.
- Raking up leaves and pruning off infected twigs and branches will also reduce inoculation. The infected material should be destroyed.
- Applying a complete fertilizer (12-12-12) will strengthen trees that are weakened by repeated bouts of the disease.
- Using fungicides (pesticides) is also a method of control but should only be used as a last resort as they can be injurious to humans, animals and plants.
If complete removal of a tree is required consider replanting with a species less susceptible to Anthracnose. (Tim’s Tip: London planetree is a good choice, and red oaks are more resistant than white oaks.)
For more information contact UNH Cooperative Extension.
Trees are a vital part of our environment. Let’s take good care of them.
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