Simetryn is a triazine herbicide that is primarily used to control
broad-leaved weeds and grass in paddy rice and other crops.
It is absorbed through roots and foliage and inhibits
Like other triazine herbicides, simetryn is characterized by high
persistence and toxicity.
Prometryn (belongs to the chemical class of sulfur-substituted triazine or thiomethyl herbicides or thio-S(symmetrical)-triazines.
Prometryn is commercially available from 1964 (in the United States
first), 6 years after the first commercial use of first chloro-S-triazines (atrazin, simazin), 8 years after the first experimental
use of atrazin, and 12 years after the discovery of herbicidal properties of S-triazines.
It is synthesized by successive N-alkylations of cyanuric acid with the addition of thiomethyl group by mercaptan.
Triazines, and concordantly prometryn, were the most applied
herbicides throughout the world in the second half of the twentieth
century for their presumably low toxicity and relatively low
environmental persistency. Prometryn was among 350 most used food
pesticides in United States (Environmental Protection Agency (EPA)
List A). However, significant evidence was gathered that S-triazines are groundwater contaminants with diverse toxic
properties (genotoxic, endocrine disrupting, and immunotoxic). This
resulted in the restricted use of atrazine and chloro-S-triazines and finally led to their complete ban in many countries.
It was believed that methylthio-S-triazines (prometryn) were less toxic but some countries also
banned prometryn together with other triazine herbicides . In 2006, there were at least 11 big manufacturers registered in
China, 7 in the USA, 2 in Taiwan and India, and at least 1 big
manufacturer in Switzerland, Israel, Italy, and Canada. Even though
banned in European countries, large areas of Asia, Africa,
Australia and Pacific region, Canada, China, India, and United
States are still treated with this herbicide. Large quantities are still being produced; for example, in 2010
one single manufacturer in China produced 20 000 tons of prometryn.
|Specifications (COA)||Assay: 95% min|
Loss on drying: 0.5% max
Acidity(as H2SO4): 0.5% max
Acetone insoluble: 0.5% max
|Formulations||95% TC, 25% WP, 13% EC|
|Target crops||Paddy, corn, soybeans, wheat, peanuts, cotton|
|Prevention objects||Gramineous weeds: Barnyard grass,Eleusine indica, Cogon, Wild oats,
Bromus, Aegilops tauschii Cosson, Foxtail, Green bristlegrass herb,
Ryegrass, Black nightshade, Crabgrass, Woodland forget-me- not,
Orchardgrass, Bedstraw, etc.|
|Mode of action||1.Selective herbicide|
3.Leaf treatment herbicide
|Toxicity||Acute oral LD50 for rats >750 mg/kg.|
Acute percutaneous LD50 for rats >1600 mg/kg.