May/June 2021 - 19

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are created (or at least registered) equal. While
they may be chemically identical, a grower
who wants to adopt a form of Integrated Crop
Management through introducing phosphite
to the fungicide program must use a product
that has a pesticide registration. OMEX®
Cell
Power Phorcephite, for example, has full U.S.
registration as a systemic fungicide for the control
of downy mildew, Pythium, Phytopthora and
other diseases, across a range of crops including
potatoes - where an added attraction is its zeroday
harvest interval.
But OMEX® also has another phosphite
registration - a product called 4pHoric. This is
registered as a fertilizer - because this is where
phosphite starts to get really interesting.
This is where we see phosphite in its double
act. Applied at high doses, it provides the
fungicidal inhibition we've just discussed. But
when applied at low levels, below that capable of
providing fungicidal activity, it can also act as a
valuable biostimulant.
Biostimulants have received increasing attention
and column inches in recent years. They're a new
class of crop protection chemicals that aren't
easily categorized, neither fertilizer nor pesticide
nor nutrient. But when applied to crops, they
can affect growth and development in numerous
ways, across the whole life cycle of the crop.
For example, some biostimulants affect seed
germination, others 'prime' defense systems or
stress responses. They can facilitate recovery
from abiotic factors, such as extremes of moisture
or temperature, improve nutrient and water
acquisition, and improve the quality of plant
produce - color or sugar content, for instance.
Some even promote better interaction between
the plant's roots and the soil microbes, in what's
known as the 'rhizosphere'.
So, what biostimulant properties does phosphite
offer the potato grower? Well, the most striking
effect is on root development, where studies
have identified that phosphite triggers a genetic
response within the plant. This prompts the plant
to reprogram its enzyme activities, stimulating
root development.
Studies have demonstrated root enhancement of
up to 50 percent in some crops. That wasn't for
potatoes, although where we've conducted our
own glasshouse trials, we've observed a useful
effect from application of a foliar phosphite
treatment at tuber initiation.
Tuber numbers increased by 12.5 percent. It's
consistent with the theory that a potato plant with
a more effective root system can support more
tubers, while the accompanying increase in root
biomass could also point - further research can
confirm - to likely benefits from improvements in
water and nutrient acquisition.
There's also evidence - the American Journal
of Plant Sciences published results from an
Argentine potato trial - that application of
phosphite to seed tubers could not only reduce
the time between planting and emergence,
but also stimulated early growth: another
biostimulant effect in action.
Will phosphite turn out to be even more multitalented?
Quite possibly: it's a fast-moving area,
and there remain many unanswered questions
about phosphite's true mode of action. There's
also the legislative aspect: the lack of recognition
for biostimulants inevitably places them in
something of a gray area, although U.S. proposals
for regulation have been tabled.
What's certain is that even with these two uses,
potato growers have a very valid reason for
using phosphite as the missing link in their 2021
agronomic armory.
Learn more at www.omexusa.com.
The product names and brands referenced here are
registered and trademarks of OMEX®
© OMEX® Agrifluids, Inc. 2021.
Agrifluids, Inc.
http://www.omexusa.com
May/June 2021

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