Hello Vincent,
I usually am not an active participant in post but I thought that I
might weigh in on your comment since I have been doing preharvest drop
research for a number of years. Jim Krupa our technical assistant has
been involved and he expressed an interest in doing an experiment to
find out a little more about why fruit drop? The experiment was done on
McIntosh and Delicious over two seasons. Briefly, 6 to 10 trees were
selected. Half were designated to be drop trees and half were
designated to be harvest trees. The experiment was carried out from the
time the first fruit dropped until most of the fruit were on the
ground. Each morning fruit under the drop tree were picked up and taken
to the lab where they were weighed and internal ethylene was determined
on each fruit. Red color, flesh firmness, soluble solids and starch
rating were determined and seed number counted. This was repeated for
fruit that dropped at 3:00 pm. Three times a week 10 fruit were
harvested from the harvest trees and similarly processed. Seed number
was not associated with fruit weight or drop although this has been
documented in the literature. I suspect that this may be an issue when
there are 0, 1 or 2 seeds per fruit but that was not the case here. The
conclusion that we came to was all fruit that dropped were climacteric
and showed signs of ripening (internal ethylene greater than 1 ppm,
increased red color and reduced starch content).
The appropriate question to ask then may be why did the fruit that
drop ripen early? We know from research done here in the 1980s that
fruit with very low seed number are also low in calcium. Fruit low in
calcium may ripen earlier. I offer another explanation.
Many of you know that recent reserach has indicated that a
carbohydrate balance deficiency in trees druing June drop is a factor
that infouences thinner response as well as the severity of June drop.
This is based on the original work of Alan Lakso and taken to the field
by Terence Robinson. The model is good and the practical application
for thinning is important. However, if one looks at the carbon balance
in Alan's model over the growing season you will note two things.
First, there is likely to be a deficit during the June drop period and
this has been highly publicized. A second period of deficit occurs at
harvest time and this has been largely ingnored. It makes perfect sense
since as fruit ripen there is a large increase in respiration
(climacteric) which fuels the synthesis of enzymes involved with
ripening. Vincent mentioned that were might be a shelf shedding
mechanism in trees. When trees have a carbohydrate deficit they must
respond. In some instances this response is shedding of fruit. Even
with fruit it is survival of the fittest. This occurs at June drop, why
not at harvest? Drop is frequently controlled by spurs. If spurs are
shaded or leaf area is small then the fruit on these spurs are most
likely to drop early. Mite damaged trees also show early drop.
We have followed drop from McIntosh over the course of the season
which often occurs over a 7 week period. Fruit increase in size about
1% per day they are on the tree. Consequently, it is not surprising
that average fruit sized will increase over the harvest season. This is
one of the attributes of using drop control compounds.
I am not sure if I have helped in this discussion but drop can be
precipitated by several events (seed number, heat, lack of light,
reduced leaf area, damaged leaves, etc) but I do believe it comes right
back to any factor that stimulates ripening will lead to increased drop.
Duane
On 1/13/2014 12:12 PM, Vincent Philion wrote:
Hello, I'm analyzing some data and I have seemingly contradictory
results. I'm hoping someone can comment and make sense of this:
For a number of randomly selected trees, fruit drop was recorded
starting late summer until harvest. For each tree, we recorded total
fruit drop (and weight), harvested fruit (and weight) and the total
(drop + harvest). As I was looking at the data, I noticed average
harvested fruit size (weight/number) was related to Total fruits per
tree... Nothing strange, until I realized harvested fruit size
INCREASED with Total fruit number on tree. As if the fruit dropping
left more energy for the remaining fruits to grow?
I was expecting harvested fruit size to be smaller on trees that had
more total fruit, not the other way around.
I'm not sure this late natural fruit drop can be compared to very late
hand thinning, but does anyone know if fruit size increase can be
linked to late thinning (notwithstanding total yield that can go down)?
Maybe this is "normal"?
Any comment welcome!
Vincent
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*Vincent Philion*,M.Sc. agr. Microbiologiste
Phytopathologiste pomiculture
*Institut de recherche et de développement en agro-environnement*
*Research and Development Institute for the Agri-Environment*
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Like most of the data I deal with, I'm best described as either "zero
inflated Poisson", or "zero inflated negative binomial". Anything but
"Normal".
Un expert est une personne qui a fait toutes les erreurs qui peuvent
être faites dans un domaine très étroit.
~ Niels Bohr
C'est pas parce qu'ils sont nombreux à avoir tort qu'ils ont raison...
~ Coluche
To call in the statistician after the experiment is done may be no
more than asking him to perform a post-mortem examination: he may be
able to say what the experiment died of.
~ Sir Ronald Aylmer Fisher
The plural of anecdote is not data.
~ Roger Brinner
The combination of some data and an aching desire for an answer does
not ensure that a reasonable answer can be extracted from a given body
of data.
~ John Tukey
Prediction is difficult, especially of the future.
~ Mark Twain (also attributed to Niels Bohr and Yogi Berra)
There are three kinds of lies: lies, damned lies, and statistics.
~ Mark Twain or Disraeli
Without deviation from the norm, Progress is not possible.
~ Frank Zappa
If you don't know where you are going, you will wind up somewhere else.
~ Yogi Berra
You can see a lot just by looking.
~ Yogi Berra
Poor, but proudly at the highest step I'm qualified for.
http://en.wikipedia.org/wiki/Peter_Principle
Inhibiteur de rodomontades depuis 1992.
Ce que l'on conçoit bien s'énonce clairement, et les mots pour le dire
arrivent aisément.
~ Nicolas Boileau-Despréaux
Vingt fois sur le métier remettez votre ouvrage
~ Nicolas Boileau-Despréaux
Keep your stick on the ice
~ The Red & Green show
Quid quid latine dictum sit, altim videtur.
~ Stéphane Laporte
Audi alteram partem
Qui potest capere capiat
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