Witches' broom is caused by a rust fungus that infects both blueberry bushes and fir trees. This disease causes clusters of small branches known as witches' brooms to form at the base of the plant.

Mites can be responsible on willow trees and honeysuckle shrubs, while phytoplasmas lead to disease in ash and elm trees. Witches’ broom can last typically for the life of the tree providing ...