October 2022 - 12

NETTING
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chemical thinning for multiple varieties.
Elsysy said the researchers also are
evaluating the relationship between seed
content and fruit quality. It has been
accepted for decades that pollination,
which leads to seed set, improves the
quality of the fruit.
So far in the MSU trial, there has not
Michigan State University researcher
Mokhles Elsysy, left, and MSU tree fruit
physiologist Todd Einhorn discuss the
utility of using nets to manage crop load
by excluding pollinators.
been a significant relationship between
the number of seeds and fruit weight and
shape, spurring interest in further review.
Initial trial results didn't show a strong
relationship between seed number and
fruit weight and shape, however, implying
the relationship is not as strong as the
scientific literature suggests, Elsysy said.
The project started in 2017 in
cooperation with Washington State
University. Evaluators netted two
different cultivars, Gala in Michigan and
Honeycrisp in Washington.
" The first objective is to reduce the
need to apply chemical thinner, " Elsysy
said. " We need to set crop load. It will
apply for everyone, but especially organic
producers. With the use of nets on the
trees, we think we can reduce crop
load and reduce the need for chemical
thinners. "
Surprise for researchers
" We did this work in 2017 and 2018, "
Elsysy said. " The results were completely
astonishing. We put on the nets so no
bees would come to the trees at all. Still,
it produced a commercial crop load. The
process between the netted and nonnetted,
in general, was very clear. When
you put the nets at different stages of open
flower or bloom, you will be able to control
crop load.
" The later you put on the nets, the less
crop load you will have, " he said. " There
are many interesting aspects we found
as we worked through this project. Why
do we have fruit when we net the tree
without any pollination or pollen transfer
happening, because there's no bees? "
Elsysy said researchers opened the fruit
thinking all of it would be seedless fruit.
" With no pollen transfer, you should get
no seeds. But, when we cut the fruit, these
fruit were full of seeds, " he said. " They are
not the same amount as the non-netted
trees, but. In Gala, you have several seeds
in the fruit, and at a little bigger stage you
can have three or four seeds per fruit. How
did these seeds develop? "
The project was extended to study the
seeds from the biggest stage of netted fruit
vs. the unnetted fruit.
" We planted the seeds and grew them
into plants. We needed to look at the leaves
to examine the geo-timing of these seeds
to be able to predict and understand what
the absence of pollen does to these fruit.
We are running this analysis now and are
waiting to see how a transfer will happen
under the nets. "
Also evaluated was the number of seeds
in the fruit and whether it changed the
fruit weight and shape.
" Usually, the higher the seed number,
Gale Gala®
CoralStar®
the bigger the fruit, but I cut many
Honeycrisp fruit with 10 seeds in them and
the fruit is still 80 or 90 grams, " he said.
" In the last two years, we've cut up
approximately 20,000 fruit. After we
looked at the effect of seed number on
shape and fruit weight, we came to the
idea that all trees have the capability of
producing seedless fruit. That's been
written in textbooks for a hundred years. "
To see how seedless fruit drop, an
evaluation was made of the trees at
fruit set, analyzing what's leading to the
Redhaven
Regina™
WE'VE GOT YOUR TREE
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12 | FruitGrowersNews.com
minimal-seeded fruits' proliferation.
" The project started as a way to mitigate
the use of chemical thinners, but now it's
opening new gates to look at how seeds
impact weight and shape, and how we
can understand better about how pollen
transfer happens without bees, " Elsysy said.
" It's written in the literature that the
higher the seed number the lower return
bloom you will have, " Elsysy said. " I
submitted a 42-page paper that challenges
the impact of seed number on return
bloom. We don't see much difference in
return of bloom. "
Researchers will attempt to determine
how " wind pollination " might impacted
the fruit, which in the trial is protected
by commercial nets that don't allow bees
to enter.
" If we could prove that wind pollination
is taking effect, that would really help us
think about the design of our orchard, " he
said. " It will help us to meet the challenge
of non-pollination years. " FGN
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October 2022

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