Tar spot is one of the most common tree fungi there is although it is almost exclusive to sycamores.
The disease is likely to be more prevalent in damp conditions so you will probably notice more cases following a wet spring and it is said to be very sensitive to air pollution so the cleaner the air, the more spots there are!
How do I recognise it?
This is an unsightly fungal disease characterised by raised shiny black spots on the leaves of Sycamores in particular and appears in late summer and autumn
Yellow spots form on the affected leaves in the spring and these develop into larger, raised black shiny spots over the summer months which can be up to 4cm in diameter. The black spots retain a narrow yellow margin.
It may cause the affected leaves to fall earlier than would normally be expected but has no long term affect on the overall tree health.
There is no chemical control available to prevent tar spot.
Recurrence of the disease in subsequent years can be reduced by clearing and burning fallen leaves. This is because the fruiting bodies develop on these leaves over the winter and the tiny spores they produce are released in spring and carried into the atmosphere in air currents to then attack developing, healthy leaves.
There are no long term health problems for the tree itself associated with this disease.
Did you know?
Tar spot was first recognised in 1794 after being discovered in Europe.