Witches Broom

A tree's shape and growing habit is developed by auxins, hormones which control the growth of new shoots. In cases of witch's broom, the normal growth of buds is interrupted, and new shoots grow sporadically. This can be caused by cytokinin, a phytohormone which interferes with growth regulation. The phenomenon can also be caused by other organisms, including fungi, oomycetes, insects, mites, nematodes, phytoplasmas, and viruses. The broom growths will continue as long as the tree lives.

Although it may cause unsightly growths in some trees, the effect is not adverse. In fact, many migratory birds and squirrels build nest in these growths as they provide a solid foundation to rest in.

If you feel your tree is diseased and devolping witches broom, check for these symptoms. - "Phytoplasmas cause either specific symptoms (virescence, phyllody, witches’ brooms) or non-specific symptoms (yellowing, reddening, reduced growth, die-back, and decline). However, symptom expression may be highly variable for a given plant–host combination. Common genus affected are elm, ash, conifer, sandal, and eucalyptus trees."

Source - Marcone, Carmine, 29 March 2021, Forests 2021, 12(4), 408; https://doi.org/10.3390/f12040408

For a professional opinion on any tree-related issues, contact Dalton Tree Consulting.

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