Witch's broom (biology)
Witches' brooms or thunderbusses are called spherical and bushy adhesions in the crowns of firs and birches .
description
While the witch's brooms occurring in firs are caused by a rust fungus with intermediate hosts from the carnation family ( pine cancer ), the birch witch's brooms are created by a simply structured type of hose fungus ( Ascomycota ), namely Taphrina betulina . This forms tiny tubes on the surface of the birch branches. As a result, it causes permanent growth disorders by repeatedly driving the birch to sprout and to form new so-called dormant buds . As a result, there is a branch addiction at the infected areas: the formation of numerous thin and short branches , which are known as witches' brooms. These structures are similar to older brooms made from a stick and birch branches. The mycelium of the fungus survives in the bark of the branches. In the crown, especially of birch trees, a lot of witch brooms can arise, which sometimes become very large. As a result, they also have a negative impact on the growth of the tree.
Witches' brooms on other hardwoods are also often caused by Taphrina species.
In larches , an infestation by rickettsia- like organisms was proven to be the cause of the witch's broom-like growth . Plant pathogenic viruses can also be the cause of some tree species such as ash and black locust . Witch's broom on apple trees, apple shoots , is a phytoplasmosis .
Witch's brooms on spruce and pine are usually not caused by parasites, but rather arise from hereditary bud mutations that are used in breeding to achieve decorative coniferous forms of small stature.
Distinction
In some places the mistletoe, which appears similar from a distance, is called witch's broom.
literature
- Fritz Schwerdtfeger : The forest diseases. Textbook of forest pathology and forest protection. Paul Parey, Hamburg and Berlin 1981, ISBN 3-490-09116-7 .
- Heinz Butin : Diseases of the forest and park trees. Diagnosis, biology, control. 2 spore boards . 3rd, revised and expanded edition. Thieme, Stuttgart and New York 1996, ISBN 3-13-639003-2 , pp. 182-185
