Biology Reference
In-Depth Information
possible control, but at least you did not have to be an organic chemist. Now
we have the following classes of fungicides:
Inorganic
Organic
Sulfur
Copper
Salts
Dithiocarbamates
Thiazoles
Triazines
Substituted
Aromatics
Dicarboximides
Dinitrophenols
Quinones
Antibiotics
Organotins
Aliphatic
Nitrogens
Benzimidazoles
Sterol Inhibitors
Strobilurins
The search for new fungicides goes on, with hundreds of synthetic organic
compounds being screened each year. This screening is often a cooperative
venture between manufacturers, state experiment stations, and the U.S.
Department of Agriculture. After safety precautions for the operator and the
environment, and the effectiveness of a compound for certain diseases have
been determined, the chief question is whether the material is phytotoxic, that
is, injurious to plants, at concentrations required for control. Phytotoxicity is
an elusive factor, not to be pinned down in a few tests. It varies not only with
the kind of plant but with the particular variety, the amount of moisture in the
soil when the spray is applied, the temperature, whether or not the application
is followed by rain or high humidity, the section of the country, and the
compatibility of the chemical with spreaders or wetting agents, as well as with
other fungicides or insecticides. Coordinated tests with new materials in
many different states are extremely valuable. Some compounds give rather
uniform results over the country; others vary widely with climatic conditions.
The 1947 Federal Insecticide, Fungicide and Rodenticide Act (FIFRA)
provides that all fungicides must be registered with the U.S. Department of
Agriculture before being marketed. Materials highly toxic to humans must be
prominently marked, instructions given for avoiding injury to plants or
animals, the toxicant chemical named, and the percentage of active and
inactive ingredients given. All labels submitted for registration must be
accompanied by proof that the claims for performance are valid.
In 1954, Public Law 518, known as the Miller Bill, was passed, providing
for tolerances. A tolerance is the legal limit of a poisonous residue, expressed
in parts per million (ppm), that may remain on an edible product at the time it
is distributed for consumption. In 1958, The Food Additives Amendment was
passed, which also controls pesticides residues in processed foods. It included
the Delaney clause, which states that any chemical found to be a carcinogen in
laboratory animals may not appear in a human food, a zero tolerance. In 1959,
the FIFRA was amended to include nematicides, plant growth regulators,
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