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nafex - Re: [NAFEX] Witches Broom

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  • From: "Kieran &/or Donna" <holycow@frontiernet.net>
  • To: "North American Fruit Explorers" <nafex@lists.ibiblio.org>
  • Subject: Re: [NAFEX] Witches Broom
  • Date: Thu, 10 Feb 2011 12:17:07 -0600

Witches broom is a word for a deformed growth on a plant. It can be a bud sport, as in many of the prostrate evergreens for sale for landscaping. People who deal with evergreens tend to watch for such a growth to make their name and possibly their fortune. Witches broom growths can indicate virus, usually that is what I think when I see them. For example, when potatoes sprout, the virused ones often have weird thin growth. Rose rosette is an example I see around here on wild multiflora roses, and sometimes on tame roses. But there are funguses that cause witches broom type growths, such as rosette in blackberries. I try to pick them out as soon as I see them so they can't spread. It's not like seeing rust and knowing the entire plant is infected forever.
The witches broom that Hector referred to also grows on the native butternut trees in this area. I have seen 2 such trees in 27 years in Tennessee. One was one of several seedlings from butternut seeds my son picked up in Vermont. Did they catch the disease from some tree off in our woods? Did it come on the seed? Donna

Some short quotes:
Diseases caused by Fungi:

Butternut canker, Sirococcus clavigignenti-juglandacearum.
This serious disease is a problem for butternuts and does not affect black or English walnuts. Symptoms include dead branches, top dieback, discolored bark which has an inky black fluid coming from cracks in the spring and sooty patches, usually with a whitish margin, in the summer. Cankers are elongated and sunken, and frequently lethal.Cutting and removing infected wood will slow the spread of infection, but there are no known controls.

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Bunch disease also attacks butternut. Currently, the causal agent is thought to be a mycoplasma-like organism. Symptoms include a yellow witches' broom resulting from sprouting and growth of auxiliary buds that would normally remain dormant. Infected branches fail to become dormant in the fall and are killed by frost; highly susceptible trees may eventually be killed. Butternut seems to be more susceptible to this disease than black walnut.




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