Nature Blog Network

tar spot disease

One of the sycamore saplings on the lane is showing the signs of tar spot disease whilst the others are free of it at present. Tar spot is caused by the fungus Rhytisma acerinum, and whilst strictly a pathogenic disease the tree can live with it quite nicely. The fungus overwinters on fallen leaves and produces new spores in the spring.

It is said that it is only in recent years that tar spot has been seen on trees in northern areas; previously it was killed off by the atmospheric pollution.

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