Sulfonylurea herbicides are highly popular and low-toxic, and are well received by people. It has been applied to a variety of crops, and some products have become the dominant species of crop field herbicides. The China Pesticide Network Xiaobian specifically introduces the mechanism, application, and development prospects of such herbicides for your reference:
It is understood that thiophenesulfuron, chlorsulfuron-methyl, etc. can be used in soybean fields; sulfonylurea herbicides used in rice fields include pyrazosulfuron-methyl, bensulfuron-methyl, ethoxysulfuron, ethersulfuron, tetrazinsulfonate Long, cyclamate, fluroxysulfuron, pyrimethanilsulfuron, etc.; corn field can be used with formamide sulfonate, nicosulfuron, chlorpyrifossulfonate, etc.; wheat field can be used methyl disulfuron, methyl iodide Sulfonamide sodium salt, flucarbazone, etc.; flusulfuron-methyl, chloropyrazine-sulfonate, etc. can be used in the high field;
The high-efficiency sulfonylurea herbicides developed by China have the monosulfimsulfuron developed by Nankai University and the thiosulfuron-methyl developed by Hunan Chemical Research Institute.
1. Mechanism of action Mechanism of action Sulfonylurea herbicides are acetolactate synthase (ALS) / acetohydroxyacid synthase (AHAS) inhibitors, which are systemic herbicides that inhibit plants ( Weeds ALS/AHAS, which prevents the biosynthesis of branched chain amino acids such as valine, leucine, and isoleucine, disrupts protein synthesis, interferes with DNA synthesis and cell division and growth, and ultimately leads to plants (weeds) death. Its basic structure consists of three parts: a reactive group, a hydrophobic group aryl group and a bridge (and an electron-transporting group). Sulfonylurea herbicides are easily absorbed by the roots and leaves of plants, and are transmitted in the xylem and phloem, and their target is acetolactate synthase.
Pharmacological characteristics Sulfonylurea herbicides have extremely high activity and low dosage. The conventional application rate is only 2 to 75 g/hm2, so it is called ultra-high efficiency herbicide, and the effect is 100 to 1000 times that of traditional herbicides. Sulfonylurea herbicides are susceptible to chemical hydrolysis and microbial degradation in soil, and due to the lack of branched-chain amino acids (proline, leucine and isoleucine) biosynthesis pathways in animals to inhibit such amino acid organisms The synthesis of herbicides as targets is highly safe for animals. Therefore, sulfonylurea herbicides are low in toxicity to mammals and safe for humans and livestock. Such herbicide products are effective in controlling broadleaf weeds, and some products have good herbicidal effects on grass weeds.
Sulfonylurea herbicides have certain selectivity for the control of weeds. Different plants have different metabolic, metabolic and degradation levels of herbicides, and the sensitivity is different. In practical use, the herbicides have a wide application time range, and are effective before and after bud treatment, and are also convenient to be combined with other herbicides to form a formulation to expand the herbicidal spectrum.
2. Problems in application At present, there are many studies at home and abroad on the mode of action of sulfonylurea herbicides and environmental behavior in soil. The research finds that there are still some problems in the application process.
Long-residue phytotoxics Sulfonylurea herbicides have made great contributions to agricultural production since their inception, but they also encountered some problems in their use. The most prominent ones are long-term residual phytotoxicity of some varieties on post-crop crops. . The main reason is that the sulfonylurea herbicide is not volatile, is not easily photolyzed, and its half-life is prolonged as the soil pH rises. Their degradation in soil is mainly through hydrolysis and microbial degradation. Soil pH and temperature are the main factors affecting the hydrolysis rate of sulfonylurea herbicides. Studies have shown that the chemical hydrolysis in alkaline soil is the slowest, equivalent to 1% to 20% of the herbicide will remain in the soil for a long time, causing phytotoxicity to the susceptible crops, the residual effect can be extended to 2 after application ~3 years.
Resistance According to the pesticide network , the resistance mechanism of weeds to sulfonylurea herbicides is divided into two types:
1 target ALS gene mutation. Mutations in the ALS gene that control weed resistance to sulfonylurea herbicides have been demonstrated in studies on Kochia. 2 non-target resistance. The non-target resistant mechanism of weeds to herbicides includes rapid detoxification of the herbicide by the plant (weed) after absorption of the herbicide to deactivate the herbicide and limit the herbicide to the site of action. This non-target resistance is less common for sulfonylurea herbicides that target a single target.
3, development and application prospects For sulfonylurea herbicides, in product development, we must pay attention to product safety and maturity of the use of technology. The registration of field effects is designed according to the pesticide field efficacy guidelines, standardized spraying, comprehensive and accurate evaluation of product safety, multi-quantity test, special attention to the safety evaluation of long-lasting herbicides for sensitive crops.
For the study of new dosage forms, the focus is on the development of new safe formulations that are easy to use, such as aqueous formulations, suspensions, dry suspensions,
a slow release agent, a water-dispersible granule, and a microemulsion without an aromatic solvent,
Reduce the drift of herbicides. In addition, the development of vegetable oil spray additives should also be strengthened.
Sulfonylurea herbicides bring good benefits to farmers and agricultural salespeople. The reduction in the cost of sulfonylurea herbicides in recent years has also led to the widespread use of this herbicide in agricultural production processes. Although some varieties of this type of herbicide will cause phytotoxicity to the post-crop crop, with the expansion of the application area, new varieties are also emerging, and there will be a large number of candidate products. Solving crop damage after cropping is the most important issue at present. As a branch of research on herbicides, safeners have attracted the attention of scholars at home and abroad. The development and application of herbicide safety agents at home and abroad, the strengthening of pesticide management, and the improvement of people's drug use, some problems encountered in the current application of sulfonylurea herbicides are expected to be solved, and have good development prospects.
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