1962, American marine biologist Carson published the book Silent Spring, which described the tragic prospect of pesticide abuse in an exaggerated way, causing strong shocks around the world. The use of pesticides once became a hot topic, and even some extremist forces advocated banning all chemical pesticides from now on. Under great pressure, pesticide researchers did not flinch. Since 1970s, by strengthening the research on legal management and scientific use of pesticides, a series of new varieties and dosage forms of pesticides with high efficiency, low toxicity, easy degradation and good compatibility with the environment have been developed, among which the most representative ones are biological pesticides pyrethroids and insect chitin synthesis inhibitors. Since then, the spring of pesticides has come.
As early as 1800, people realized the insecticidal function of pyrethrum, and as an insecticidal plant, it was introduced to all parts of the world for large-scale cultivation. 1942, Swiss chemists Stodinger and Lauska first published the chemical structure of pyrethrins. 1949, the first pyrethroid pesticide, allethrin, was synthesized by American chemist Xie kete and others. However, allethrin and a series of pyrethroid pesticides discovered later are easily decomposed by light, so they are only used for indoor pest control, not for agricultural pest control in the field. 1973, Elliott of Lausanne Experimental Station in England successfully synthesized the first photostable pyrethroid-permethrin, which made a breakthrough contribution to the application of pyrethroid pesticides in agricultural production.
Compared with other organic synthetic pesticides in the same period, the dosage of pyrethroid pesticides is greatly reduced. For example, the dosage of deltamethrin per hectare is only 15g, which is 100 times higher than the conventional dosage, while the toxicity to mammals such as human beings and livestock is reduced by 432.3 times (transdermal toxicity) and 43.6 times (oral toxicity) respectively. In addition, pyrethroid pesticides are similar in structure to natural pyrethroids and are easy to degrade in the environment. Because of these excellent advantages, the research and development of pyrethroid insecticides has become a craze since 1980s. At present, there are more than 40 commercialized varieties, accounting for 25% of the total use area of agricultural pesticides, and they have become the main pesticide varieties for controlling agricultural and forestry health pests.
Insect chitin synthesis inhibitor is an insect growth regulator. In the early 1970s, when van de Alen and others were screening new herbicides, they assumed that the combination of diuron and diuron might have higher herbicidal activity, so they removed two methyl groups on diuron and replaced benzonitrile with benzoyl to synthesize DU- 19 1 1. However, contrary to expectations, Du-1911did not show herbicidal activity, but it was unexpectedly found that it could affect the chitin synthesis of insects and lead to the death of Pieris rapae larvae. This great discovery led to the development of a large class of new pesticides. Insect chitin synthesis inhibitors are called "biological pesticides" because of their unique mode of action and high insecticidal activity, which are low toxic to mammals, safe to fish, natural enemies of pests and bees, and do not have to worry about residual toxicity and environmental pollution. Over the past 30 years, diflubenzuron, diflubenzuron, chlorfluazuron, mirex and other 10 varieties have been commercialized and become new "weapons" to protect crops.
With the development of pyrethroids and insect chitin synthesis inhibitors, some fungicides and herbicides with high internal absorption efficiency and low toxicity have come out one after another, such as ergosterol inhibitors such as triadimefon, benzimidazole fungicides such as metalaxyl and carbendazim, and sulfonylurea herbicides such as chlorsulfuron. Because the pesticide efficacy developed in this period was greatly improved, the dosage in the field was greatly reduced, which effectively reduced the adverse effects and residual toxicity of pesticides on the environment.
Since 1970s, breakthroughs have been made in the research and development of biogenic pesticides, especially in the development and application of agricultural antibiotics and live microbial pesticides. Agricultural antibiotics are secondary metabolites with pesticide function produced by microbial fermentation, such as kasugamycin, mirex and validamycin used as fungicides, pyridylphosphine used as herbicide, gibberellin used as plant growth regulator, and avermectin, which is considered to be the most exciting pesticide in the field of pesticides in recent years.
Live microbial pesticides, that is, using some microorganisms that are pathogenic to harmful organisms as pesticides, multiply their living bodies in large quantities through industrial methods and process them into preparations, such as commercial Bacillus thuringiensis (Bt), Beauveria bassiana, nucleopolyhedrosis virus, granulosis virus, pathogenic nematodes, microsporidia and so on. Because biological pesticides come from nature, they are easy to degrade naturally in the environment and have no pollution to the environment, so they show broad application prospects.
Since the 1990s, biotechnology has been applied to the field of pesticides and made outstanding achievements. For example, Bacillus thuringiensis preparation (Bt) is a kind of insecticide which has special effects on LEPIDOPTERA pests and is safe for beneficial organisms and people and animals. However, due to the great influence of ultraviolet rays on living microorganisms, it is difficult to give full play to its efficacy in the field. Recently, people have transferred the toxin gene of Bt insecticidal protein into Pseudomonas fluorescens, so that Pseudomonas fluorescens can produce Bt insecticidal protein. Because the pigment produced by Pseudomonas fluorescens can prevent the destruction of insecticidal toxin by ultraviolet rays, the field efficacy of Bacillus thuringiensis preparation (Bt) can be greatly improved. What's more, people have successfully transformed the modified Bt protein toxin gene into tobacco, tomato, cotton and other crops, and obtained insect-resistant plants. There is no doubt that biotechnology has given pesticides a new meaning.
With the progress of society and the rapid development of science and technology, pesticides are constantly developing and improving. At present, pesticide varieties are developing in the direction of high efficiency, low toxicity, low residue and environmental compatibility. The creation of pesticides also broke through the traditional concept of directly killing pests, emphasizing that the use of pesticides has a moderate long-term impact on the physiology or behavior of pests, that is, the role of pesticides is not to directly kill pests, but to control their harm by regulating their growth, development and reproduction. In terms of pesticide application technology, "environmentally compatible dosage forms and pesticide application technology" has been put forward in recent years, which greatly improves the deposition rate of pesticides on the target, greatly reduces the dosage of pesticides and reduces the impact on the environment. In addition, with the improvement of pesticide safety risk assessment and management, bio-rational pesticides will become an irreplaceable weapon for people to fight pests. As N.E.Borlaug, winner of the Nobel Peace Prize in 1970, predicted, "Our first task is to eat and keep healthy, so we must have pesticides. Without pesticides, the world will starve! "