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  • From: Richard Moyer <ramoyer@gmail.com>
  • To: nafex@lists.ibiblio.org
  • Subject: Re: [NAFEX] Fireblight on Korean Giant pear (long)
  • Date: Sun, 9 May 2010 08:26:42 -0400

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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