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Tar Spot of Sycamore

Symptoms

Large, slightly raised, black shiny blotches that develop on the leaves assist with recognising sycamore tar spots. The tar spots can measure up to about 1.5 centimetres. Though when looking at the leaf and identifying the tar spots all over it, the leafs’ tissue still remains in good vigour.

Cycle of Infection

A tar spot will affect tree in the spring. It is a recurring infection, a cycle that lays dormant through the winter before producing spores it the spring, ready to infect. The spores can be spread mostly by the wind and little air born insects.

Implications for host

Tar spot on the leaves make the leaves fall off prematurely and can disfigure the tree. Though this is not always the case, because tar spot does not necessarily infect the trees vigour. The fallen leaves that are infected, if not raked up, will produce spore in the spring. The spores are covered in a glutinous solution which will adhere to young leaves as they start to grow.

Treatments

There is no treatment available for this disease, though when the leaves have fallen in autumn, it is a good idea to rake them up and dispose of them. The best way of disposing them is by burning, or by making leaf compost. The idea of this is to stop the spores developing on the fallen leaves in the following spring.

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