Blueberry Disease - Witch's Broom
I emailed the Cheryl Smyth from University of New Hampshire Cooperative Extension and Plant Disease Lab about this disease I have been seeing in blueberry plants. Here is the information she gave me about this disease:
"The excessive branching in the blueberry is called witches’ broom. The disease is caused by the rust fungus Pucciniastrum goeppertianum. The alternate host of the fungus are fir tree (Abies spp.) (balsam fir is most common in your area). Foliage does not usually develop on the brooms. Heavily infected plants may have reduced fruit production, or in severe cases, no fruit at all. The fungus produces spores on the swollen stems in the spring. The spores infect developing fir needles. In the summer, spores produced on the fir needles infect blueberry leaves and stems. Management recommendations include removing the fir alternate host within 500 yards of the blueberry planting (fir trees are native to you area of NH, thus this cannot be done practically). Since the infection is systemic in the plant, simply cutting out the distorted shoots will remove the
symptomatic shoots, but new distorted shoots will appear in following years. Plants with brooms at the base of the plant should be removed and replaced. Although the disease is systemic, infected plants can survive for many years. (although fruit production will likely be reduced.) The one cultivar reported to be resistant to infection is not suitable to NH growing conditions. There are no effective fungicidal controls for the disease."
Thanks to Cheryl for this helpful information! Its good for us to be able to understand how a disease works so we can use preventative measures to keep from spreading and infecting other plants. I've included pictures of infected plants below.
My suggestion to people with this disease on their blueberry bushes would be to wash hands, tools, and clothes after working around your blueberry bushes during spore production and before visiting other geographic places with blueberry bushes and/or fir trees to keep the fungal spores from spreading and to use specific care when disposing of any part of this plant. It sounds like we can cut the infected parts off - but it will not get rid of the disease, only clean the plant up a little and perhaps help keep spore production down.
"The excessive branching in the blueberry is called witches’ broom. The disease is caused by the rust fungus Pucciniastrum goeppertianum. The alternate host of the fungus are fir tree (Abies spp.) (balsam fir is most common in your area). Foliage does not usually develop on the brooms. Heavily infected plants may have reduced fruit production, or in severe cases, no fruit at all. The fungus produces spores on the swollen stems in the spring. The spores infect developing fir needles. In the summer, spores produced on the fir needles infect blueberry leaves and stems. Management recommendations include removing the fir alternate host within 500 yards of the blueberry planting (fir trees are native to you area of NH, thus this cannot be done practically). Since the infection is systemic in the plant, simply cutting out the distorted shoots will remove the
symptomatic shoots, but new distorted shoots will appear in following years. Plants with brooms at the base of the plant should be removed and replaced. Although the disease is systemic, infected plants can survive for many years. (although fruit production will likely be reduced.) The one cultivar reported to be resistant to infection is not suitable to NH growing conditions. There are no effective fungicidal controls for the disease."
Thanks to Cheryl for this helpful information! Its good for us to be able to understand how a disease works so we can use preventative measures to keep from spreading and infecting other plants. I've included pictures of infected plants below.
My suggestion to people with this disease on their blueberry bushes would be to wash hands, tools, and clothes after working around your blueberry bushes during spore production and before visiting other geographic places with blueberry bushes and/or fir trees to keep the fungal spores from spreading and to use specific care when disposing of any part of this plant. It sounds like we can cut the infected parts off - but it will not get rid of the disease, only clean the plant up a little and perhaps help keep spore production down.