The contribution of chemical pesticides is universally recognized. Because the use of chemical pesticides effectively controls the diseases, insects and grass damage of crops, the world loses 30% to 40% of the total crop yield every year, and recovers economic losses of 300 billion USD/a, more than 20 kinds of insects and mites. Diseases that seriously threaten human health are also effectively controlled. According to the World Health Organization, the use of DDT to control malaria mosquitoes, from 1948 to 1970, saved 50 million people from death and reduced the number of patients with various diseases by 1 billion. In 2000, the global import reached 6.4 billion, and the population Growth has caused the world to face problems such as food shortage and lack of nutrition. According to the current population growth rate, the world population will reach a peak of 8.5 billion in 2035. If the crop output is not increased by two to three times, one third of the forest and grassland still covered by the earth will be reclaimed as farmland. Produce food. According to statistics, there are 742 diseases, 838 pests, 704 weeds and 20 species of rodents There are more than 100 kinds of insects and grasses. Due to the use of pesticides, some common pests and diseases have been effectively prevented. The annual loss of food can be about 31.5 million t/a, and the loss of cotton is 1.15 million t/a. The loss of oil is 1.5 million t/ a, to recover economic losses of 30 billion yuan / a. China is a developing country with a population of 1.3 billion. The existing cultivated land area is 95 million hm2, and the per capita possession of cultivated land is only 0.073 hm2, which is far lower than the world average. It should occupy 7% of the world's cultivated land and feed the world. More than % of the population, the pressure of agricultural production is self-evident. In order to meet people's demand for agricultural products such as grain, fiber and oil, it is necessary to continue to develop agricultural production. Chemical pesticides are the most important and most effective means of plant protection. The sustainable development of agriculture must make rational use of chemical pesticides to prevent and control the harmful populations and avoid or reduce crop losses. 3. Trends in chemical pesticides <br> For early pesticide and chemical control, N. Morgan has proposed the "three E" theory, namely Effetiveness, Efficiency, and Environment. Effetiveness refers to the efficacy and effect of chemical pesticides, including positive effects and negative effects. Positive effects are well known. Negative effects refer to phytotoxicity, poisoning problems, residues, damage to beneficial organisms and resistance. Efficiency refers to the use efficiency, such as less consumption, less energy and water consumption, high utilization, and high control efficacy. Environment refers to the agricultural regional environment. For a long period of time, people developed chemical pesticides according to the "three E" theory, avoiding a large number of negative effects caused by the manufacture of raw materials, preparation processing, and final application. With the introduction of “green pesticidesâ€, today's chemical pesticides pay more attention to efficiency, safety and economy. The future trend of plant protection is to control the damage caused by pests within a certain threshold, adjust the density and quantity of harmful populations, ensure the diversity of organisms and ecological balance, and never kill pests. Therefore, future pesticides will be environmentally friendly or environmentally compatible. The main role of pesticides is to influence, control and regulate the growth and reproduction processes of various pests, so that pests can be controlled without harming human health and not destroying the ecological environment. The future trends in chemical pesticide development are:
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1. Factors affecting sustainable agriculture
Sustainable agriculture is one of the major issues that the world is seriously thinking about. People hope that the "Green Revolution" will save the planet. It is hoped that through such a revolution, while improving the ecological environment, improving economic efficiency, and taking social responsibility, more agricultural products will be produced to meet the growing needs of the population. However, many ecological and environmental problems that have occurred in the world have had a serious impact on the sustainable development of agriculture, such as: 1 due to reclamation of farmland, construction of houses, deforestation caused by forest destruction; 2 forest and water body population reduction, some species extinct, organisms Diversity is facing serious threats or serious damage; 3 farmland desertification, salinization and soil erosion; 4 fresh water and seawater are polluted, causing food reduction; 5 high residual organic pollutants, fertilizers, organic chlorine, heavy metals and volatile organic matter Enter the ecosystem. 6 Changes in climatic conditions cause many other changes, such as floods, droughts, sea level rise and the spread of infectious diseases; 7 the burning of oil and forests leads to the accumulation of greenhouse gases (such as CO2, NOX, SOX, etc.), causing atmospheric warming and greenhouse effect. . The global ecological problems that have emerged have attracted people's attention and are looking for various solutions to solve ecological and environmental problems. Protecting the planet we live in is the most important issue of our time.
2. Chemical pesticides and production agriculture
In 1962, American woman writer Rackel Carson published "Silent Spring" (SilentSpring), a book that said pesticides kill wild animals, endanger children's health, and contaminate the table. Leading the public to blame on pesticides, and also leading people to re-recognize pesticides. Chemical pesticides, like other chemical substances, naturally have some negative effects on the ecological environment, such as: 1 high-toxic pesticides such as methamidophos, parathion, methyl parathion, phosphonium, monocrotophos in the manufacture and use In the process of causing poisoning; 2 killing beneficial organisms, such as natural enemies, birds, aquatic animals, cockroaches, etc.; 3 production process discharge pollutants; 4 part of the pesticides in use and a large number of aromatics and other solvents into the environment, only China's entry into the environment Aromatic hydrocarbons such as toluene and xylene reach about 260,000 t/a; 5 parts of high-residue pesticides remain in agricultural products, affecting the quality of agricultural products; and 6 pesticides cause phytotoxicity.
Under the pressure of safety, environment and ecology, governments have formulated a series of very strict laws and regulations on chemical pesticides, and have imposed many restrictions on the production and application of chemical pesticides. Some even put forward the absolute requirements of “zero risk†and “zero residue†for pesticide production and use. In order to meet the requirements of ecological agriculture, in recent years, people began to study "Green Pesticide" ("Green Pesticide"). Reduce or eliminate the application and generation of hazardous materials in the design, manufacture and use of chemical pesticides. The research and development, production and application of pesticides are using high technology, and chemical pesticides are changing in the original medicine , Liu type and application methods. These changes include: (1) improve the inherent activity of the original drug; 2 improve the efficacy and effectiveness of the use of pesticides; 3 reduce the amount of pesticides; 4 improve the safety of humans, animals and crops; 5 improve the compatibility with the environment; Negative effects of non-target organisms and the ecological environment. After the 1960s, a batch of highly toxic, high-residue organochlorine, organic mercury and organic arsenic preparations were banned. In 1983, in order to meet the needs of sustainable agriculture, China officially banned organochlorine pesticides such as BHC and DDT. It has also formulated a series of regulations and regulations on pesticide management, production and use, and has established strict pollutant discharge standards, strengthened monitoring and emission management of pollutants, to ensure that the ecological environment does not continue to deteriorate and gradually improve. To ensure the sustainable development of China's agricultural production. A large number of high-efficiency, low-residue organophosphorus, carbamate, pyrethrin, organic nitrogen, and heterocyclic pesticides have been successfully developed and put on the market. At the same time, a number of bio-sourced pesticides such as Jinggangmycin have been researched and developed. , Liuyangmycin, etc., the amount of pesticides dropped from tens of kilograms per square meter to several hundred grams, or even a few grams. In the process of pesticide production, a large number of new technologies and new processes have been adopted, which greatly improved the output and quality of the products, reduced the consumption of raw materials, and reduced the emissions of the three wastes. Pesticide preparations followed by emulsifiable concentrates, liquid preparations, concentrated emulsions, wettable powders, powders, dry suspensions, granules, aerosols, and smoke agents, and developed seed coatings, effervescent tablets, aqueous emulsions, aqueous suspensions, New dosage forms such as microemulsions, dry suspensions, water-dispersible granules, and dry seed dressings. It not only improves the effectiveness and efficiency of chemical pesticides, but also greatly improves the environmental quality. In 2000, China's pesticide raw material production capacity has reached 800,000 t / a, more than 270 varieties, the output of about 500,000 t / a, the output ranks second in the world, does not meet the domestic market demand, and there are 100,000 tons per year. /a around the exit, the processing capacity of the preparation is about 1.3 million t / a, the output is nearly 1 million t / a, the variety of preparations more than 1900. The research, development, production and application of chemical pesticides in China have gradually adapted to the requirements of sustainable agriculture.
1) Pesticides with unique mechanism of action will be hot spots - such as insect growth regulators, plant growth regulator pheromones, sex hormones, etc.;
2) Natural plant pesticides, microbial pesticides, and biological control agents are valued;
3) Chemical pesticides will be developed to be highly efficient and ultra-efficient, for example, to develop active compounds with a dose of only a few grams per square meter, using a single optically active compound of high purity;
4) Water-soluble powders, aqueous suspensions, water emulsions and other aqueous preparations which are free from oiling, dust-free, easy to use and diversified in preparation, will be used;
5) New methods and technologies will be adopted for the research and development of new pesticides. Such as combinatorial chemistry, high-throughput screening, robotic automation, etc.
6) Biotechnology will be widely used in the development of new pesticides. The future development direction of chemical pesticides is a world concern. If the merger and reorganization of major pesticide companies in the world can predict the future development direction of the pesticide industry, the combination of traditional chemistry, innovative chemistry and bioengineering will be the progress of chemical pesticides. Develop and open up broader prospects. The 21st century is the century of life sciences. In recent years, some famous chemical pesticides have been researched and developed. For example: imidacloprid and its homologs, rutin and its homologues, methoxy acrylates and their homologs, imipenone and its homologs, and the like. The introduction of these varieties, the breeding of genetically modified crops, and the emergence of a new bactericidal "Bion" that does not kill pathogens and stimulate plant disease resistance are successful examples of the combination of chemistry and biotechnology. Imidacloprid is a major breakthrough in the structure of nicotine. It is of epoch-making significance. Azoxystrobin is a biomimetic synthesis. Mithium is mainly used in larvae and has a unique mechanism of action. Some chemical pesticides developed in recent years generally have low toxicity to in and out of animals. It is safe for beneficial organisms, aquatic organisms, not accumulating in living organisms, and not in the environment, and is in line with the development direction of modern chemical pesticides.
4. Chemical pesticides will play an important role in sustainable agriculture
The factors affecting sustainable agriculture are multi-faceted. Solving the problems faced by sustainable agriculture requires the joint efforts of professionals in many fields to ensure the sustainable development of agriculture. Plant protection is an important link advocated by plant protection. In the comprehensive prevention system, chemical pesticide control has an irreplaceable role because:
1) Agricultural control measures - planting disease-resistant, anti-viral, insect-resistant crop varieties, reforming farming systems, etc. are all defensive measures, not enough to prevent the harm of diseases, insects, grasses and rats.
2) Although biological control measures have the characteristics of controlling pests and diseases and reducing environmental pollution, the use of live insects and live microorganisms is demanding, and if the ecological conditions are not suitable for the release area, this measure will lose its significance. 1992 The World Conference on Environment and Development proposes to control the sale and use of chemical pesticides worldwide. By 2000, biopesticide production accounted for 60% of total pesticide production. However, by 1999, global biopesticide Sales accounted for only 9% of total pesticide sales.
3) Physical control measures, such as trapping, capturing and other means, have more problems and it is difficult to achieve control effects. Chemical pesticide control is the most convenient, most effective, most reliable and cheapest means in the comprehensive prevention and control of agricultural diseases, pests and diseases. Especially in the event of sudden, invasive biological disasters, there is no other way to replace chemical pesticides. Despite the rapid development of insect-resistant and herbicide- tolerant GM crops, it is expected that chemical pesticides will remain an important means of supporting sustainable agriculture in the next 50 years. The future chemical pesticides face many challenges, but the advancement of science and technology and the demand for agricultural production also provide opportunities for the development of chemical pesticides. Chemical pesticides continue to play a major role in sustainable agriculture.