Taphrina betulina is a fungal plant pathogen that causes the gall, witches broom, which is a chemical infection of birch buds or the developing shoots, leading to a proliferation of growth.

Witches broom on birch trees (Betula species), are dense bunches of stunted twigs which look like birds nests.

The gall starts as densely packed clusters of buds which can remain for many years.

Possibly, when the fungus loses vigour, the buds grow into many slender shoots.

[5][6] Taphrina betulina has been recorded from Europe, New Zealand and North America.