Page 14 - Griffin Gazette Issue 3 - 2021

HOW DOES PHOSPHITE WORK?
The active ingredient phosphite directly
inhibits growth of the pathogens, but there is a
second important mode of action for this class
of fungicides– they are also biostimulants.
Phosphite, like other biostimulants, elicits the
plants’ own natural defenses through multiple
series or cascades of metabolic changes in the
plant. Altogether the effect of these changes is
known as Systemic Acquired Resistance. Just
one of the many significant chemical markers
of SAR activity in plants is an increase in the
level of Indole-3-Acetic Acid (IAA) produced.
Research has shown phosphite-treated plants
produce excess of IAA compared to untreated
plants. The path winds on…IAA is not well
known in commercial horticulture outside the
lab, yet IAA is the predominant natural rooting
hormone in plants. It was discovered long
before the more familiar IBA we routinely use to
kick start the rooting of cuttings. So phosphite
fungicides not only protect roots, they promote
root growth by inducing the plant to produce
more IAA. That is why you may hear GGSPro
recommending a phosphite fungicide to
improve weak or damaged roots. Think of it as
a bonus the next time you select a preventative
fungicide, or think of it as a tool when needed.

Products List: Aliette, Areca, Fosphite,
OxiPhos, Phostrol, TKO Maxx (TKO Phosphite)

Images: Poinsettias treated with a phosphite fungicide (right in
each picture) show increased lateral roots, height, and maturity
just 4 days after treatment. All plants, control (left) and
phosphite-treated, were also innoculated with a Trichoderma-
based biofungicide prior to treatment. | Photo credit: Joe Moore,
Lucas Greenhouses

14 | GRIFFIN GAZETTE 2021