Witches` broom
Witches’ broom A witches’ broom is a growth form characterized by a proliferation of clustered branches with short internodes. They are usually caused by: a disease infection an insect infestation an insect or mite-vectored disease a genetic mutation Back to stem and leaf modification menu Next Back to vegetative parts main menu Main menu Witches’ broom Pathogen-induced This eastern ninebark (Physocarpus) forms a witch’s broom when severely infected with the powdery mildew fungus Sphaerotheca macularis. Back to stem and leaf modification menu Back Next Back to vegetative parts main menu Main menu Witches’ broom Insect-induced The honeysuckle witches’ broom aphid (Hyadaphis tararicae) is true to its name and causes clusters of deformed stems in honeysuckle (Lonicera). Back to stem and leaf modification menu Back Next Back to vegetative parts main menu Main menu Witches’ broom Insect (mite) and disease - induced The witches’ broom seen in hackberry (Celtis) is caused by the association between an eriophyid mite (Eriophyes celtis) with the powdery mildew fungus Sphaerotheca phytophila. Back to stem and leaf modification menu Back Next Back to vegetative parts main menu Main menu Witches’ broom Insect (mite) and disease – induced The Protea witches’ broom was thought to be induced by the Eriophyid mite Aceria proteae. However, it appears that the mite is the vector for a phytoplasma that is the causal agent for the multiple shoot phenotype. Back to stem and leaf modification menu Back Next Protea cynaroides Back to vegetative parts main menu Main menu Witches’ broom Insect and disease - induced Aster yellows is a plant phytoplasma vectored by the aster leaf hopper (Macrosteles quadrilineatus). One of its symptoms on members of the Asteraceae is a characteristic witches’ broom. Aster yellows in purple coneflower (Echinacea). Back to stem and leaf modification menu Back Next Back to vegetative parts main menu Main menu Witches’ broom Genetic mutation Witches’ brooms often occur as a specialized bud sport in woody plants. It is particularly common in conifers. Witches’ broom in hemlock (Tsuga). Back to stem and leaf modification menu Back Next Witches’ broom in pine (Pinus). Back to vegetative parts main menu Main menu Witches’ broom Genetic mutation Propagation of a stem from a witches’ broom can directly lead to a new, slower growing, dwarf cultivar. Pinus nigra ‘Globosa’ originated from a witches’ broom. Pinus nigra ‘Globosa’ Back to stem and leaf modification menu Back Next Back to vegetative parts main menu Main menu Witches’ broom Genetic mutation This dwarf ginkgo was originally propagated as a cutting from a witches’ broom. Ginkgo biloba ‘Mariken’ Back to stem and leaf modification menu Back Next Back to vegetative parts main menu Main menu Witches’ broom Genetic mutation This group of spruce (Picea) seedlings was derived from witch’s broom seeds. They show the diversity seen in witches’ broom-derived seedlings, but also demonstrates that the original witches’ broom was from a heritable mutation. Back to stem and leaf modification menu Back Back to vegetative parts main menu Main menu
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