Agriculture Reference
In-Depth Information
They are used as selective preemergent and postemergent herbicides to control
broadleaf weeds and woody plants
Mode of Action
These compounds act by inhibiting nucleic acid synthesis, which in turn
interferes with protein and enzyme synthesis and metabolism.
Toxicity
Some formulations may cause severe to moderate skin and eye irritation
and permenent damage.
Table 5.24
Commercial products containing pyridinoxy and picolinic acid
herbicides.
Active Ingredient
Trade Names
Clopyralid
Lontrel, Reclaim, Stinger
Fluroxypyr
Starane
Picloram
Grazon, Tordon
Triclopyr
Garlon, Grandstand, Rely
t.
Triazines
The triazines were developed by the Swiss firm, J. R. Geigy Limited, in
1952. Two well-known examples of this group of heterocyclic compounds
are simazine and atrazine. These are persistent soil-acting herbicides which
can be applied in large concentrations as total weed killers on rights-of-way or
industrial sites. At lower concentrations, they can be used for selective con-
trol of germinating weeds in a variety of crops. They are taken up by the
roots of emerging weed seedling, causing it to turn yellow and die, but owing to
their low solubility in water, they do not penetrate to the deeper levels of the
soil and consequently have little effect on the deep rooted crops.
Triazines are used selectively on certain crops and nonselectively on oth-
ers. They are used in greatest quantity in crop production and are used nonse-
lectively on industrial sites.
Prometryne is used for selective pre- and postemergence control of annual
weeds in vegetables, cotton, and sunflowers. Desmetryn provides postemer-
gence control of annual weeds. Methoprotryne, ametryn, dipropetryn, ethiozin,
terbutryn, cyanazine, and eglinazine-ethyl provide effective control of grass
weed in cereals. Aziprotryne is used for weed control in a wide range of vege-
tables and acts through both the soil and foliage. Metribuzin and metamitron are
used for pre- and postemergence weed control.
Altogether some 25 triazines are currently used as commercial herbicides,
and the most important is atrazine.
