How to Manage Pests

Pests in Gardens and Landscapes

Witches' broom

Witches' brooms are dense clusters of twigs or thickened stems that develop on the branches of woody trees. Leaves and shoots may become distorted, dwarfed, and discolored. Witches' broom results from diseases such as powdery mildew or rusts, mistletoe, or from insect and mite feeding. Herbicides also can cause witches' brooms to form.


Provide plants with proper cultural control to keep plants vigorous. Prune out witches' brooms at least several inches below where they form.

Witches' broom symptoms on oak
Witches' broom symptoms on oak

Statewide IPM Program, Agriculture and Natural Resources, University of California
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