Agriculture Reference
In-Depth Information
cidal actions against spider mites. Figure 5.10 shows the product with the
trade name Benlate, which contains benomyl.
Mode of Action
Uptake occurs via the roots and leaves, and transport occurs by way of the
xylem. The active compound which is transported is the methylbenzimidazole
carbamate (MBC or BCM). In plants the active compound is readily formed
by hydrolysis. It is not clear whether a further cleavage occurs or if this
cleavage occurs in the plant or fungal cells.
Benzimidazoles primarily act on cell and nuclear division. Nuclear divi-
sion is inhibited by the binding of the MBC to the microtubular proteins in-
volved in the synthesis of the mitotic spindle apparatus.
Benomyl has an extremely wide spectrum of activity and can be used as a
leaf fungicide, seed disinfectant, and soil treatment.
Carbendazim, which is the common name used for the active agent MBC
or BCM, is also marketed as a fungicide. It exhibits a wide spectrum of activity,
is used to control snow molds, and is used in stem injections to inhibit Dutch
elm disease.
Fuberidazol is used to combat snow mold, and mainly in combination
with other substances for cereal seed stock disinfection. It was one of the first
organic fungicides able to replace organic mercury as a seed protectant.
Thiabendazol is also used to disinfect cereal seed stock in combination
with other fungicides. It is used to control snow mold, bunt, and loose smut
in wheat and barley, as well as stripe disease in barley. It is also used as a
spraying agent against eyespot in cereals and against ear mildew and Septoria.
In potatoer, thiabendazol is used as a spraying agent to control Fusarium dry
rot. Like benomy, this compound has a very wide spectrum of uses.
Toxicity
Benomyl is a synthetic, organic fungistat having little or no acute toxic
effect in mammals. No systemic poisonings have been reported in humans.
Although the molecule contains a carbamate grouping, benomyl is not a cho-
linesterase inhibitor. It is poorly absorbed across skin; that which is absorbed
is promptly metabolized and excreted.
Although injuries to exposed individuals have been few, dermal sensitiza-
tion has occurred in agricultural workers exposed to foliage residues.
Thiabendazole is widely used as an agricultural fungicide, but most expe-
rience with its toxicology in humans has come from medicinal use against
intestinal parasites. Oral doses administered for this purpose are far greater
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