According to the release characteristics of the active ingredients of pesticides, the sustained release dosage forms of pesticides can be divided into two types: free-release conventional and controlled release dosage forms. According to reports, the utilization rate of conventional pesticides is only 20% to 30%, and the loss rate through various channels is as high as 50% to 60%, which is not only economically wasteful, but also causes large-scale environmental pollution. Therefore, controlling the release amount, release time and release space has always been an important direction for the research of new formulations of chemical pesticides.
The core of the controlled release technology is to make the polymer compound interact with the pesticide. The active ingredient of the pesticide will be released into the environment continuously and slowly according to the preset concentration and time (according to the needs of pest control), and can be maintained for a long time. A certain concentration. Therefore, the sustained release dosage form of pesticides can make the performance of the drug more stable due to the protective effect of the high molecular substance, and reduce the influence of environmental factors such as water and air. Secondly, the sustained release technology can greatly extend the special effect period of the same dose of the pesticide, thereby Reducing the number of pesticides used and the total amount of pesticides, the possibility of residue and environmental pollution is significantly reduced; again, slow release technology can reduce the toxicity and phytotoxicity of pesticides.
The existing pesticide sustained release dosage forms can be classified into physical sustained release agents and chemical sustained release agents. The physical sustained release agent means that the active substance is "dissolved" in the polymer or mixed with the polymer by other physical methods, and can be divided into microcapsules, inclusion compounds, multilayer articles, hollow fibers, adsorbents, A foam, a solid solution, a dispersion, a composite, or the like. The chemical sustained release agent refers to a polymer which combines an active material with a polymer by forming a chemical bond or a polymer of the active material to form the active material, and can be classified into a self-polycondensate, a direct bond, and a bridging combination. . Among the commercially available pesticide sustained release agents, most of them are physical types, and various physical types are mostly microcapsules. According to the type of pesticides, pesticides have the most sustained release dosage forms, followed by herbicides and fungicides, and the least amount of regulators.
Since the introduction of microencapsulated methyl parathion in Pennwalt in the United States in 1974, sustained-release technology has received extensive attention in the pesticide industry. More than 20 products have been introduced, but the yield is not large. China has also produced methyl parathion and phoxim microcapsules for a time, for various reasons, has not been promoted. In general, the development of sustained-release agents is slow, due to the high cost of the capsular material, the high cost of the preparation, and the lack of competitiveness.
1. Research and application of slow release pesticides
1. Screening of sustained release materials
In view of the high price of existing slow-release pesticides, Beijing Agricultural Technology Extension Station based on the successful research on “controlling seed delay germination technologyâ€, using natural polymer materials with low cost and easy availability as controlled release materials, through special processing Process and processing equipment and pesticide composition complexes, using bioassay and chemical titration to determine the release concentration and speed of slow release pesticides, has been selected for a series of sustained release materials - including uniform release and non-uniform "S" curve release The sustained release material, the uniform release means that the concentration of the active ingredient of the pesticide released from the sustained release material to the environment at the same time is the same; the release of the non-uniform "S" curve refers to the release of the active ingredient of the pesticide from the sustained release material into the environment. The speed increases continuously over time, and after reaching the maximum value, it continues to decrease over time, releasing an "S" curve. By adding some biodegradable polymer materials to the slow-release pesticide complex, the release rate of the pesticide can be adjusted, so that the release dynamics of the pesticide are consistent with the production needs; the slow-release pesticide complex is made into pellets, and then in the pellet The surface of the grain is coated with a polymer film, and the active ingredient of the pesticide is released into the environment absorbed by the crop through the degraded pores of the polymer film, so that the release of the controlled release pesticide can be controlled for a longer period of time.
2. Application in the prevention and control of vegetable diseases and insect pests
A systemic insecticide such as imidacloprid or acetyl is compounded with a sustained-release material and processed into a sub-pill or granule for roots having a sustained release property. When the crop is planted or transplanted, the active ingredient of the medicament is slowly released from the sustained-release carrier material, and the water transpiration through the crop leaves is transmitted upward along with the moisture to reach the leaf to control the pest. Because of the low number of pests in the early stage of pests and the fact that the pests are at a young age, there are drugs to prevent and control. Therefore, the low-dose drug can reach the prevention and treatment index, and the drug can be applied in a single-time concealed application through the root, and the natural enemies of the pesticide and the pest are protected. The results of field trials for the control of radish amaranth showed that the root pellets had a certain effect on the emergence rate, and the sustained-release granules had no effect on the emergence of seedlings. The sustained-release Aketai granules were applied at 675 g/hm2, 45 after application. In days, 55 days and 80 days, the effects of controlling mites were 90.9%, 100.0% and 80.0%, respectively, while the same dose of conventional AKT was applied to the soil. The control effects of 45 days, 55 days and 80 days after application were respectively 55.3%, 23.0% and 0.0%, it can be seen that after the Aktaya sustained-release material, the efficacy and duration of the effect are greatly improved. The results of field trials using slow-release Aketai to control tomato whitefly showed that the control effects were 75.0%, 80.0% and 70.0%, respectively, 30 days, 44 days and 58 days after application, which solved the difficulty in controlling whitefly. The problem has reduced the cost of manual drugs. It can be concluded that the use of slow-release pesticides for one-time concealed application can prevent the harm of whitefly, aphids and other pests throughout the growth period of vegetables.
3. Application in cotton dwarfing
The use of defoliation to shape plant types, control apprentices, promote early maturity and increase production on cotton has become a routine cotton planting measure and has played an important role in production. Especially in the inland cotton area of ​​Xinjiang, China, the current "dwarf, dense, early, membrane" cultivation method is based on the control of the system of shrinking and stagnation, because it is possible to reduce the dwarfing effect. Increase planting density to create conditions for early maturity. However, it should be pointed out that the use of the squash is always based on foliar application, while the effective period of foliar application is 15 to 20 days. Therefore, in a growing season of cotton, it is generally required to spray 2~5 times of shrinkage according to the seedling condition and climatic conditions, which not only increases the labor input, but also is not conducive to the standardization of technology. If the controlled release technology can be used to control the release amount, release time and release space of the active ingredient, it is possible to control the growth of the whole growth period of the cotton plant by one application (shrinking), thereby simplifying the cotton management measures.
Based on the research of sustained-release materials, the application of slow-release anneal coating to seed granulation and root-release squash granules on cotton was explored. To continue to control cotton growth. The results of field trials showed that the granulation of slow-release squash seed granules can achieve the effect of conventional spraying 4~5 times in controlling cotton growth. For example, the test results in Beijing area indicate that the plant height of cotton can be controlled at 60~ 80cm, the control is 140cm; the test results in Manas County, Xinjiang showed that the cotton plant height can be controlled at 50~60cm and the control is 110cm. In the case of seed treatment only, the elongation and growth of all main stem internodes and fruit branches are continuously controlled, indicating that the technique can be used to achieve a one-time reduction. That is, the purpose of controlling the growth of cotton plants during the whole growth period. After the technology of slow release and shrinkage is improved, it can not only simplify the production management measures of cotton, but also facilitate the standardization of cotton chemical control technology, thus speeding up its promotion. The test also proves that the addition of insecticides in the slow release mites can greatly reduce the insect pests in the cotton seedling stage. If the fungicide is further added, it is expected to prevent or reduce the disease at the seedling stage. This will further simplify the cultivation and management measures of cotton and have broad application prospects.
4. Application of slow release dwarfing agent on the lawn
The high cost of maintenance and management of lawns and the large amount of water consumption are hot issues of concern to the society. The trotters, bactericides, and the like are processed into root granules having a sustained release property, applied to the surface of the lawn or applied to the bottom of the lawn when the lawn is laid. The results of field experiment showed that both application methods can achieve the effect of controlling turf growth. One application can control the growth of turf for 1~2 years, the frequency of lawn pruning is significantly reduced, and the water consumption of turf is reduced, the resistance is enhanced, and the resistance is resistant. Green.
Second, summary
The sustained release dosage form of pesticides adapts to the increasingly strict environmental protection needs; the application of controlled release of pesticides opens up a broad prospect for the field of chemical pesticides, which has caused major changes in the structure of traditional pesticide varieties, from free release to controlled release. The transformation of the type, function and instrumental drug integration direction is strictly controlled according to the dosage, time and action point used, so that some old pesticide varieties that have been eliminated have new vitality and become new, efficient, safe and economical pesticides. In China, we have also done research and research on the chemical slow release agent of pentachlorophenol, and produced microcapsules such as parathion and phoxim. However, since China is a big agricultural country, from the perspective of developing agricultural production and protecting the ecological environment, it is necessary to vigorously develop and develop high-efficiency, safe, economic and convenient green pesticides to improve the overall level of China's pesticide industry.
As an emerging technology, slow release technology is not very mature in theoretical research and practical operation. There are many problems that need to be solved, such as high processing costs, and the final destination of polymers is difficult to predict. Despite this, slow release technology has attracted more and more attention from experts in the field of agriculture and is forming a new field of research. It is believed that through the joint efforts of agricultural science and technology workers, the technology will be fully applied in agriculture.
(Beijing Agricultural Technology Extension Station îž‘ China Agricultural University)
ã€Comment】 ã€Print this article】 ã€Close this page】 ã€Large, medium and small】
DQOK Bathroom Single Cold Basin Faucet With Simple And Unique Design, DQOK Basin Faucet Created According To People's Living Habits, Create High Cost Performance Modern /Classical High-quality Brass/304 stainless steel Faucets Makes You Creat A Wonderful And Conformtable Bathroom. DQOK Bathroom Basin Faucets Have CUPC, NSF/ANSI 61, Low-Lead,SASO,KC and CE certificates.
Single Cold Basin Faucet,Matte Black Basin Faucet,Button High Basin Faucet,Handle Single-Cold Basin Faucet
Heshan Dingquan Sanitary Ware Industry Co., Ltd , https://www.dqokfaucets.com