Agriculture Reference
In-Depth Information
Commercial products that are currently available include Polybor, and Py-
robor.
Toxicology and Mode of Action
Borates are absorbed by the plant roots and translocated throughout the
plant. They are nonselective and persistent herbicides. Borates accumulate in
the reproductive structures of the plant, but the precise mode of action is un-
clear.
Formulated as powders and solutions and often mixed with other herbi-
cides; they are spread or sprayed as nonselective herbicides.
Dust formulations are moderately irritating to skin. Inhaled dust causes
irritation of the respiratory tract, cough, and shortness of breath.
As mentioned earlier in Section IV, Insects, there have been few poison-
ings from the pesticidal uses of borates. Most poisonings have resulted from
injudicious uses in human medicine aimed at suppressing bacterial growth,
such as compresses for burns. Many poisonings of newborns occurred in the
1950s and 1960s.
d.
Clorates
The chlorates are unstable molecules and strong oxidizing agents. They
are highly flammable when in contact with organic materials and sometimes
ignite spontaneously. Some formulation contain flame retardants, such as
sodium metaborate.
Sodium chlorate has been used widely as a soil sterilant. It is readily ab-
sorbed by the roots and leaves and may be translocated throughout the plant.
Its mode of action is not well understood and may be related to the high oxi-
dizing capacity of the chlorate ion.
Magnesium chlorate is used as a defoliant and dessicant.
2.
Organics
a.
Aliphatic acids
Mode of Action
TCA,
the sodium salt of trichloroacetic acid, is primarily employed to
control monocotyledons. Uptake of the highly water-soluble trichloroacetate
takes place mainly via the roots or rhizomes. The active substance is concen-
trated in the growth-active areas, and symptoms of wilting, dark green discol-
oration, or even of leaf deformation may occur. The plants finally begin to
die after several days.
