Anthracnose Disease in Plane Trees
Anthracnose refers to a group of diseases caused by fungi with similar structures. The diseases will cause leaf blight on most trees but usually will not cause severe damage. However, anthracnose will cause significant damage to members of the Platanus genera or plane tree family. Does this Spark an idea?
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Facts
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Anthracnose in plane trees is caused by the Apiognomonia veneta strain of fungus. Water propagates the fungus and the weather impacts the severity of the disease. Frequent rain and low temperatures promote anthracnose, with maximum damage occurring when the temperature is between 50 and 55 degrees F. As the temperature rises from 55 to 60 degrees, the intensity of the disease decreases. It does very little, if any, damage once the temperature rises above 60 degrees.
Types
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The American sycamore, London plane and Oriental plane are all members of the plane tree family. The American sycamore is the most susceptible and the Oriental plane is the least susceptible to the disease. The Bloodgood, Columbia and Liberty varieties of the London plane tree are resistant to anthracnose.
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Identification
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Disease symptoms for plane trees include irregular brown lesions along the leaf veins to the leaf edges. New leaves will wilt rapidly, which is often confused with frost damage. Cankers may develop along the twigs and branches of the affected leaf clusters. Larger branches may also develop cankers.
Effects
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The cankers result in injury to the bark, destroying membranes that conduct water and minerals from the roots to the leaves and return the food produced by the leaves to the roots. This is also known as girdling. Girdling may eventually cause the death of twigs and branches. Repeated annual killing of the twigs will result in what is known as a witch's broom--a cluster of dead twigs and live branches. The disease can also cause defoliation.
Treatment
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Fungicide sprays should be applied to new swelling buds. During the rainy season, additional applications are recommended at seven- to 14-day intervals. If defoliation occurs early in the season, a second set of leaves may develop from mid-June into July. Fungicide sprays should be applied to the new leaves.
Non-chemical prevention methods include pruning, gathering and burning affected leaves and twigs, and cutting the cankers out of large limbs. The cankered tissue should be removed down to the healthy wood. Plant plane trees that are resistant to anthracnose.
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