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nafex - Re: [NAFEX] Black-knot disease and fire-blight - effects trunk and limbs, or just branches?

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  • From: Douglas Woodard <dwoodard@becon.org>
  • To: North American Fruit Explorers <nafex@lists.ibiblio.org>
  • Subject: Re: [NAFEX] Black-knot disease and fire-blight - effects trunk and limbs, or just branches?
  • Date: Mon, 28 Nov 2011 00:55:16 -0500

Steve, black knot most commonly infects the branches, but I have seen it on a Myrobalan rootstock at ground level.

Re fireblight: hereabouts the most common route of infection is through secondary blossom due to its timing, but if there is a wound lower down it can enter there. The level of nitrogen fertilization has a very large effect on susceptibility to fireblight infection. I've seen a heavy fireblight infection in a young block of Bartlett, attributed to the nitrogen fetilizer applied to a field across a farm lane which had been planted to sweet corn. Similarly, previously healthy old trees of Sheldon which became badly infected after being partly topworked to Bosc and fertilized. Careless pruning is deadly as fireblight is easily transmitted on tools.

Doug Woodard
St. Catharines, Ontario, Canada


On 11/28/2011 12:11 AM, Steven Covacci wrote:


Group:
I have a question re: black-knot in stone fruits/(Prunus spp.) and
fire-blight in pomes/(Pyrus, Malus, Sorbus).
If your'e variety of tree is very black-knot or fire-blight prone, and you
decide to top-graft it with another variety which is not disease prone, will
black-knot/fire-blight yet effect the trunk and limbs of the initial variety;
or does it ONLY effect the tips, so regardless of the degree of
susceptibility of any part of the tree bellow the branches (rootstock, trunk,
limbs), it will only effect the tree if the branches are of a disease-prone
variety?
Thanks,
Steve; NJ



  • Re: [NAFEX] Black-knot disease and fire-blight - effects trunk and limbs, or just branches?, Douglas Woodard, 11/28/2011

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