Blueberry witches broom

Blueberry witches broom is a systemic fungal disease caused by the rust fungus Pucciniastrum goeppertianum. This pathogen specifically targets plants within the Ericaceae family, most notably wild and cultivated blueberries, lingonberries, and cranberries, causing severe vegetative proliferation.

The disease is characterized by the formation of dense clusters of thin, stunted, and highly branched shoots, commonly referred to as "witches' brooms." These abnormal growths occur because the fungus disrupts the host plant's hormonal balance, redirecting the flow of nutrients away from healthy fruiting buds to the infected areas.

Visual symptoms include the stunted broom-like structures which often persist throughout the growing season. During the sporulation phase, you may observe bright orange or brownish spore masses appearing on the leaves or the stems of the affected branches. As the disease progresses, these parts of the plant often succumb to necrosis.

The epidemiology of the fungus is unique as it requires an alternate host to complete its life cycle, specifically fir trees (genus Abies). Aeciospores produced on fir needles are wind-dispersed to blueberry plants. High humidity and cool temperatures are ideal conditions for the successful germination of these spores on young succulent shoots.

Management of this condition focuses on cultural control methods. Growers must regularly monitor their plantations and prune out any symptomatic branches at the first sign of infection. Removing all infected material from the site is essential. Furthermore, planting berries away from known stands of fir trees can significantly reduce the pressure of this fungal pathogen.