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  • From: David Malas <info4today@yahoo.com>
  • To: North American Fruit Explorers <nafex@lists.ibiblio.org>
  • Subject: Re: [NAFEX] Fireblight on Korean Giant pear (long)
  • Date: Mon, 10 May 2010 06:25:48 -0700 (PDT)

Regarding fire blight.

I stumbled upon this statement while reading a book on grafting techniques. I
got the book at the Minneapolis / Hennepin County Libraries:

The Plant Propagator's Bible, by Miranda Smith, page 112. Copyright 2007.

"Rootstocks determine many of a plant's characteristics, including size,
productivity, pest and disease resistance, fruit quality and stress
tolerance. Consequently, there is no faster or more certain way to change or
modify some basic qualities of the original plant. Perhaps you want to grow
an apple that is notoriously susceptible to fire blight. By grafting a scion
of the cultivar to a resistant rootstock, you'll have a much greater chance
of being able to grow a healthy tree that never attracts this disease."

The book jacket says, "Miranda Smith has been teaching horticulture for more
than 30 years. She's had the luxury of gardening in most climatic zones in
North America...Smith is author or co-author of 13 books about horticulture
including...'Rodale's Pest and Disease Problem Solver'( Rodale, 1995)"

Based on what Miranda Smith says, my thinking would be to propagate cuttings
of trees that you find are highly resistant to fire blight, and use these
rooted cuttings as the rootstocks for varieties you are having problems with.
I'm sure this is nothing newsworthy to those of you who are in the "old pro"
category (and you are likely way beyond this) but for a few of us, I thought
Smith had an interesting comment.

David Malas,
Minneapolis, USDA Zone 4



--- On Sun, 5/9/10, Richard Moyer <ramoyer@gmail.com> wrote:

> From: Richard Moyer <ramoyer@gmail.com>
> Subject: Re: [NAFEX] Fireblight on Korean Giant pear (long)
> To: nafex@lists.ibiblio.org
> Date: Sunday, May 9, 2010, 7:26 AM
> Donna,
> To identify Korean Giant (KG) or Shinko:
> Shinko ripens earlier, late July-early Aug in NE TN vs
> late
> August-Sept for KG.  Seeds need to be black all over
> before
> harvesting, else you get ‘tree potatoes’.  At our
> place, KG has
> blighted, but less so than about 10 other ‘blight
> resistant’ Asian and
> Euro pears, planted or grafted about the same time. 
> Depending on
> fruit set, or lack of thinning, both KG and Shinko can
> range from
> small apple size to over a pound each.  So size not
> the best
> indicator, particularly with single trees.
>
> While it’s possible that KG could be the least resistant
> pear in your
> collection to this years blight, under your conditions, it
> is
> generally recognized in much of the country as having a
> fairly high
> degree of blight resistance.  Would be helpful to have
> the Southern
> Pear Interest group members weigh in with their
> experiences, can’t
> remember why but some of them do not favor KG.  Also,
> degree of blight
> resistance data from commercial growers or research plots
> with many
> more trees than you or I is helpful for any general
> conclusions.
>
> My recollection of this data is that KG is more resistant
> than many
> other Asian pears, at least in parts of the upper south,
> Atlantic
> region and midwest.  But in certain (not all) blight
> years, I have had
> a bit of blight on KG.  I try to keep my trees growing
> slowly, though
> tough with the vigorous KG, to minimize blight pressure.
>
> I’ve not noticed blossom blight on KG as you have this
> year; mine only
> on growing tips of vigorous new wood.  But for both
> you and I, data
> points are too few to draw general conclusions.
>
> Ed Fackler noted research in the NE that identified at
> least 7 strains
> of fireblight, which could explain why the trees that do
> blight vary
> with location or from year to year.
>
> Further reasons not to generalize from single tree data:
> I have three KG trees, each on OHxF333 rootstock, the
> younger two
> grafted from the original.  Call them A, B and
> C.  A (original from
> Fackler) been bearing heavily and regularly for about 16
> years.  No
> blight for a dozen or so years, even as I was losing a few
> apple and
> pear trees to the ground, but has blighted a bit on 1-2
> year wood,
> occasionally, since then.  B and C are about a dozen
> years old.  B has
> never blighted, but C has, even into 3 year old wood. 
> But AS A GROUP,
> they are the most blight resistant pears we grow.  How
> resistant?
> Depends on the tree and the location.  C is more
> stressed than B,
> which could explain why it’s more susceptible though both
> are vigorous
> growers.  Don’t know.  This is why I’m
> reluctant to conclude and
> declare degrees of blight resistance from a single tree.
>
> Of the 30 or so pear trees I just grafted, about half are
> KG.  Will
> see how they do in time, being 30 miles from first
> location, with
> different soils, slope and aspect.
>
> Richard Moyer
> SW VA
> Fishing for morels this afternoon, another fruiting
> kingdom.
>
> Donna wrote:
> I've got fire blight down here.  Not exactly sure why,
> it seems to have
> > gotten started during a dry spell, and the weather was
> quite dry while the
> > trees were blooming.  One thing is for sure,
> Korean Giant pear is NOT
> > resistant to fire blight.  Lucky in Hopkinsville
> KY and someone in
> > Chattanooga have both told me that theirs died to the
> ground from blight.
> > Mine bloomed nicely this year, but most of the fruit
> spurs have blighted.
> > I've been pulling them off and cutting off branches,
> I'd like a real crop
> > before it dies.  It's grafted about 3 ft high and
> there's a branch I've
> > already grafted something else to.
> >
> >   A number of my apples have the blight
> too.  I really thought I'd have a
> > crop this year.  Now I wonder what my trees will
> look like when it's done.
> > Donna
>
> But Richard,  You're the one who sent me Korean
> Giant.  Or that's what I
> think it is.  You sent 2 sets of scions, and I grafted
> 3 trees.  Two I had
> labeled as Korean Giant, and one as Shinko.  I
> happened to be paying
> attention to whether Asian pears were leafing out with or
> without a green
> cast, trying to figure out whether I had Henderson or
> Hartwell pears, and
> noticed that I must have done the labels wrong on the trees
> from you.  The
> two trees I had labeled as Korean Giant came out
> differently, so I figured
> once I had fruit that there were 2 Shinkos and one
> KG.  The fruit on the odd
> tree out was bigger with a greenish cast to the skin under
> the russetting
> that made the fruit look more bronzey.  The other two
> trees made lighter
> fruit, smaller and lots more of it.  They are hardly
> touched by the blight.
>    So here are my questions:  Did you
> have a third variety of Asian pear
> that was susceptible to blight?  Or if we're just
> having a bad infestation
> of blight this year, am I going to find that it stops on KG
> after some minor
> damage?  I'm not too worried about it on some pear
> varieties that I know are
> very resistant, but some of the apples I really don't know
> much about as far
> as FB is concerned.
>    The UT pear releases I'm not worried
> about.  They tested their seedlings
> by grafting Bartlett or Clapp's to the young trees, and
> infected the graft
> the next spring.  The seedling had to stop the FB from
> growing any further.
> I understand that Magness would not have passed this
> test.  Spalding bloomed
> for the first time this year so I'm curious to see what it
> does.  It is susc
> in GA I have read.  Personally I was looking forward
> to actual fruit this
> year, not just data.    Donna
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