Maine Organic Farmers and Gardeners Association
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Prune Witches' Broom from Blueberry Plants

Witches' broom on highbush blueberry

Witches' broom on highbush blueberry

November 1, 2018

Witches' broom is a fungal disease that causes thickened, rubbery growth with odd-looking leaves on branches and in the crown of blueberry plants. The bark is light tan, cracked and shriveled, and infected shoots never fruit. Plants can be heavily infested with the systemic disease (it moves through the plant) but still produce a reasonable crop, although plants slowly become less productive. Remove canes where the broom occurs, and destroy those canes. If brooms arise from the base of the plant and no new, uninfected canes are growing, replace the bush. Autumn is a good time to look for infected canes: They're easy to see when leaves have dropped, and you can prune and burn them in the wood stove now. Balsam fir is the alternate host for this disease; on these trees, the disease simply causes small spores on the underside of leaves and is not problematic. Read more in "Growing Highbush Blueberries" in The Maine Organic Farmer & Gardener.

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