The most common signs of Sycamore Anthracnose are:
- *Heavy leaf and twig drop in late spring
- *A thinning crown
- *Random, dead leaves in canopy
- *Distorted limb growth
- *“Witches’ broom” growth (dense clusters of twigs)
- *Cool, wet, spring weather will aggravate the spread of this disease.
If the average daily temperature at the time of leaf budding is below 55 °F, anthracnose infections will be severe. If the average daily temperature is 60F or above during this time, disease incidence will be greatly reduced.
Sycamore anthracnose is caused by the fungus Apiognomonia veneta and is more serious than anthracnose on other shade trees. Sycamore anthracnose is common when cool, wet weather occurs during leaf development. Considerable defoliation may occur in late spring, however trees normally bounce back and produce a second set of leaves in early July that are disease-free. Leaves that are infected in early spring often turn brown and shrivel while still small, which can be mistaken for frost damage. Leaves that are infected may have brown foliar lesions that follow along the veins in V-shaped patterns. Leaves turn brown and may drop prematurely or continue to hang in the tree.
There are two other stages of this anthracnose: shoot and leaf blight and canker formation. Shoot and leaf blight results when the pathogen enters young, succulent shoots. It causes the rapid death of growing shoots and leaves. The pathogen overwinters in twigs and is active whenever temperatures are high enough in the fall, winter and spring. During winter, cankers form on infected shoots and kill the buds. Repeated infection results in deformed shoots and witches brooms. Although this disease can weaken the trees and increase their susceptibility to attack by other pathogens and pests, it is not lethal.
Management: Dead twigs should be pruned as they develop throughout the growing season. Rake and discard fallen leaves to reduce the source of the fungus. It is impractical to spray fungicides on large trees, however for smaller, specimen trees, the disease can be controlled with fungicides applied at three intervals; just before bud break, during bud break, 10 to 20 days later. Systemic fungicide injections can also be used.
If you really want to plant a Platanus species and don’t want to worry about sycamore anthracnose, plant a hybrid planetree, which are resistant to the disease. These trees are mixed with a maple.
EXCLAMATION LONDON PLANETREE Platanus x acerifolia ‘Morton Circle’ Zones 4-8
OVATION LONDON PLANETREE Platanus x acerifolia ‘Morton Euclid’ Zones 5-7
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