Hello, David —
Did you apply any postharvest treatments to the affected fruit? Do the spots
appear at points of fruit contact in the boxes as the fruit come out of
storage? If answers to these two questions are positive, then toxicity from
postharvest treatment solutions due to slow drying at contact points might be
involved. If answers to the first two questions are negative, then my final
question is whether you applied calcium sprays in the field during late summer?
As you can tell, I don’t know the cause of the damage shown in your photos.
However, I have received or been sent photos of similar problems from many
growers and consultants over the past 5 to 8 years. As you indicted, I have
frequently noted what appears to be damage originating from a lenticel but then
spreading to kill epidermal cells around the affected lenticel. In those
cases, I suspect (but cannot prove) that the damage resulted from uptake via
the lenticels of some toxicant (calcium, captan, other pesticide, air
pollutants?) that weakened but did not immediately kill the cells around the
lenticel. However these weakened cells later died during storage, resulting in
blackened lenticels. And I suspect that diffusion of the toxicant from the
lenticel entry point slowly killed other epidermal cells around that lenticel.
In some cases, the toxicant may have been applied in a postharvest treatment,
but I suspect that most damage of this kind is initiated in the field. Your
photos, especially the one showing damage on the calyx points of the fruit,
suggests that sprayed product may have pooled at the low points of the fruit
during a preharvest spray, thereby allowing for excessive uptake that
contributed to subsequent cell death during storage. In some cases, I have
wondered if fruit that are too close to a sprayer nozzle during late season
sprays may end up with lenticels that are damaged by direct exposure to the
high-pressure output from passing nozzles, but I doubt that was the case for
your fruit where single lesions seem to predominate.
I wish we knew what the offending toxicants and/or contributing factors really
are. Or, if anyone has a better explanation for the damage in the photos, I
would love to hear it.
Dave Rosenberger, Plant Pathologist,
Hudson Valley Lab, P.O. Box 727, Highland, NY 12528
> On Nov 28, 2015, at 2:16 PM, David Kollas <kol...@frontier.com> wrote:
> The two photos here show a skin-deep discoloration now appearing in several
> varieties of our stored fruit
> (32-36F, air). In most cases I can distinguish a circular lighter-colored
> zone centered on a lenticel, but this often merges into similar tan-colored
> skin beyond the single lenticel. None of the spots I have seen is larger
> than the
> the diameter of a 5-cent coin. Affected skin is not different than normal
> skin to the touch. There is no pitting or
> depression in the affected area. Note that in one of the Mutsu fruits shown,
> discoloration is limited to the calyx-end points.
> In several years I have seen scald symptoms near the end of storage season
> (late February, March), but
> now in mid-November, I don't expect to see superficial scald. I am wondering
> whether others have seen
> similar symptoms.
> David Kollas
> Kollas Orchard
> Tolland, Connecticut; USA
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