''Taphrina betulina'' is a fungal

plant pathogen Plant pathology (also phytopathology) is the scientific study of diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomyc ...

that causes the

gall Galls (from the Latin , 'oak-apple') or ''cecidia'' (from the Greek , anything gushing out) are a kind of swelling growth on the external tissues of plants, fungi, or animals. Plant galls are abnormal outgrowths of plant tissues, similar to be ...

, witches broom, which is a chemical infection of

birch A birch is a thin-leaved deciduous hardwood tree of the genus ''Betula'' (), in the family Betulaceae, which also includes alders, hazels, and hornbeams. It is closely related to the beech-oak family Fagaceae. The genus ''Betula'' contains 30 ...

buds or the developing shoots, leading to a proliferation of growth. It was first described by Emil Rostrup in 1883 and is found in Europe,

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

and North America.

Description

Witches broom on birch trees (''

Betula A birch is a thin-leaved deciduous hardwood tree of the genus ''Betula'' (), in the family Betulaceae, which also includes alders, hazels, and hornbeams. It is closely related to the beech-oak family Fagaceae. The genus ''Betula'' contains 3 ...

'' 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. In the spring, asci form on small leaves which grow on the shoots. These leaves usually fall before the normal leaves grow elsewhere on the tree. There can be several witches broom in a tree. Witches broom, formed by ''Taphrina betulina'' can be found on dwarf birch (''

Betula nana ''Betula nana'', the dwarf birch, is a species of birch in the family Betulaceae, found mainly in the tundra of the Arctic region. Description It is a monoecious, deciduous shrub growing up to high. The bark is non-peeling and shiny red-copper ...

''), '' Betula nana x pubescens'', silver birch (''

Betula pendula ''Betula pendula'', commonly known as silver birch, warty birch, European white birch, or East Asian white birch, is a species of tree in the family Betulaceae, native to Europe and parts of Asia, though in southern Europe, it is only found a ...

''), downy birch (''

Betula pubescens ''Betula pubescens'' (syn. ''Betula alba''), commonly known as downy birch and also as moor birch, white birch, European white birch or hairy birch, is a species of deciduous tree, native and abundant throughout northern Europe and northern Asia ...

'') and ''Betula pubescens'' var.''glabrata''. A

phytoplasma Phytoplasmas are obligate intracellular parasites of plant phloem tissue and of the insect vectors that are involved in their plant-to-plant transmission. Phytoplasmas were discovered in 1967 by Japanese scientists who termed them mycoplasma-lik ...

can also form similar looking witches broom on birch. Witches broom also grow on

hornbeam Hornbeams are hardwood trees in the flowering plant genus ''Carpinus'' in the birch family Betulaceae. The 30–40 species occur across much of the temperate regions of the Northern Hemisphere. Origin of names The common English name ''hornbeam' ...

(''Carpinus'' species) and cherry (''

Prunus ''Prunus'' is a genus of trees and shrubs, which includes (among many others) the fruits plums, cherries, peaches, nectarines, apricots, and almonds. Native to the North American temperate regions, the neotropics of South America, and the p ...

'' species); caused by '' Taphrina carpini'' and '' Taphrina wiesneri'' respectively.

Distribution

''Taphrina betulina'' has been recorded from Europe, New Zealand and North America.

References

Taphrinomycetes Fungi described in 1883 Fungi of Europe Fungi of New Zealand Fungi of North America Galls {{fungus-tree-disease-stub