Rhytisma acerinum, commonly known as sycamore tar spot, can be seen on trees throughout the country. During the summer, Rhytisma acerinum manifests itself as raised black spots on the leaves of sycamore trees. Although slightly detrimental to the aesthetics of the tree, this fungal infection does not have any significant affect on the health of established specimens.
The black spots found on the leaves are the fungal fruiting bodies. When the leaves fall in the autumn, the fungus continues to live in the foliage detritus on the ground. Airborne spores are released from the fungus in the detritus during the spring, and attach themselves to new leaves and the life cycle continues.
To reduce the affects of infection, removing fallen leaves from the vicinity of the tree and burning them will kill the fungus as it over winters. This method will only reduce the level of infection. To completely eradicate the infection, all sycamore leaves would need to be removed from the area surrounding the tree, which of course would be almost impossible. The airborne spores can after all travel as far as the wind blows!
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