The contribution of pesticides to humans is obvious to all. Over the years, pesticides have played a prominent role in promoting agricultural production and income, bringing more food to humans and improving the quality and level of our lives. In the current agricultural production, agriculture has not been replaced for a long time, and the use of pesticides has always had sharp contradictions with environmental protection. This article intends to provide a comprehensive introduction to some basic knowledge such as the classification, selection and use of pesticides, so that readers can better and rationally use pesticides and protect the environment.
First, the classification of pesticides
1. Classification by nature can be divided into chemical pesticides, microbial pesticides and plant pesticides.
(l) Chemical pesticides. Can be divided into two major categories of organic pesticides and inorganic pesticides. Organic pesticides are a class of organic compounds that are capable of killing pests and regulating their growth and development through artificial synthesis, such as dichlorvos, dicofol, triadimefon, trifluralin, tetramine, 2,4-D, and the like.
Inorganic pesticides, including natural minerals, can be used directly to kill harmful organisms. Such as sulfur, copper sulfate, zinc phosphide and the like.
(2) Microbial pesticides. These kinds of pesticides are beneficial microorganisms that are toxic and killing to pests and diseases, including bacteria, fungi, viruses, etc., and are processed by a certain method, such as Bacillus thuringiensis, Beauveria bassiana, and nuclear multi-angle. Body virus, etc.
(3) Plant pesticides. This is a kind of medicine made from plants, such as fish vine, tobacco, pyrethrum and so on.
2. According to the purpose classification, it can be divided into insecticides , fungicides, acaricides, rodenticides, herbicides and plant growth regulators.
(l) Insecticides and rodents. According to its action mode on insects and rodents, it is divided into stomach poisons, contact agents, fumigants, repellents, antifeedants and the like.
(2) fungicides. According to its mode of action on pathogenic microorganisms, it is further divided into protective fungicides, therapeutic fungicides and eradicators.
(3) Herbicides. According to its performance and mode of action, it is also divided into killing and systemic herbicides.
Each pesticide has a suitable control object and scope, and there is no “universal medicineâ€. For example, insecticides can only control pests, and fungicides can only prevent diseases. The same insecticides have different properties of the pesticides, and the objects for controlling pests are different. For example, insecticides with strong stomach toxicity are only chewing mouthparts such as cabbage caterpillars that bite the stems, leaves and roots of crops. , tobacco budworms, etc. are effective, but have little effect on pests of sucking mouthparts; same as fungicides, some have special effects on fungal diseases, some have special effects on bacterial diseases; some have herbicides on dicotyledons Weeds are effective, and some have no obvious effect on dicotyledon weeds or do not kill grass. Therefore, when selecting pesticides, it is necessary to first determine what diseases, pests and diseases occur, and then determine the correct pesticides according to the diseases, insects and grasses that occur.
3, according to the dosage form classification, can be divided into old dosage emulsifiable concentrate (EC), suspending agent (Suspension ConcentrateSC), 3, emulsion emulsion (Emulsion in waterEW) and microemulsion (MicroemulsionME), wettable powder (WP), water-based (also known as water-based) dosage form and water-dispersible granules (WDG).
Agro-pharmaceutical is the process of processing a specific chemical or a mixture thereof that is usually biologically active into a product suitable for the desired environment and exerting optimal biological performance; adverse effects on the applicator and the environment and harm to crops To the lowest limit.
(1) Old-type EC (EC) EC is a commonly used pesticide formulation, which contains a large amount of organic solvents such as xylene, which wastes petroleum resources and causes environmental pollution, and is transported and stored due to the flammability of the solvent. And the choice of container is also limited.
(2) Suspension Concentrate SC is a solid or insoluble or slightly soluble in water. Stable liquid solid state system. The suspending agent is usually composed of an active ingredient, a dispersing agent, a thickening agent, an anti-precipitating agent, an antifoaming agent, an antifreezing agent, and water. The content of the active ingredient is generally from 5% to 50%. The average particle size is generally about 3 μm. The dispersing agent has better dispersibility and spreadability, high suspending rate, strong adhesion to the surface of plant body, and resistance to rain erosion, so the efficacy is more significant than that of wettable powder. In the preparation of pesticide suspensions, it should be noted that: (1) the selected active ingredients are relatively stable to water, and the size of the original drug does not change during storage; (2) the viscosity of the preparation is suitable for low, and does not change with storage temperature. And change; (3) better naturally dispersed in water, and the diluent is relatively stable. Since the pesticide suspension agent is always present in the form of a concentrated suspension, chemical instability may occur during storage, especially for long-term storage, and in addition, physical stability problems are more often present. This usually involves three aspects: (1) flocculation and aggregation due to interaction between particles; (2) austenite crystal growth; (3) delamination and particle deposition due to gravity. To maintain the physical stability of the pesticide suspension during storage, it is necessary to control the accumulation, sedimentation and crystal growth of the suspension through formulation and processing.
(3), Emulsion in water EW and Microemulsion ME have received much attention. Water emulsions (dense emulsions) and microemulsions are prepared by dispersing liquid or semi-solid pesticide active ingredients in water, and the active ingredients must be stable in water for a long time. Under intense agitation, the original drug is dispersed in water by means of a suitable emulsifier, and then a milky or transparent liquid prepared by adding an auxiliary agent such as a stabilizer or an antifreezing agent is a stable dispersion system. The difference between the water emulsion and the microemulsion is that the particle size of the active ingredient dispersed in water is different, the former is 0.1-50 μm, and the appearance is milky white; the latter particles are ultrafine, 0.01-0.1 μm, and the appearance is transparent or nearly transparent. The amount of emulsifier required to formulate a microemulsion is usually greater than the amount used to formulate an emulsifiable concentrate or water emulsion, sometimes up to 30%. Therefore, microemulsions are currently only suitable for high value-added crops such as fruit trees and vegetables.
Suspoemulsion SE is made up of water-insoluble pesticide raw powder and crude oil. It is formulated into a stable high-suspended emulsion system with water as a dispersion medium by means of various auxiliaries. It consists of an opal phase and a continuous phase, both of which have one or more active ingredients, but the active ingredient in the continuous phase is in the form of a solid dispersion. Therefore, it has the advantages of suspending agent and water emulsion, avoids the poisoning of pesticides and wettable powders to operators by organic solvents and dusts, and environmental pollution, and is safer to store and transport, and has excellent performance and high biological activity. The efficacy is also relatively long lasting. The suspending agent will gradually replace the wettable powder and become the main dosage form of the pesticide, and drive the development of pesticide dosage forms such as suspending agent (SE), water emulsion (EW) and water dispersible granule (WDG).
(4), wettable powder (WP)
(5), water-based (also known as water-based) dosage form and water-dispersible granules (WDG).
The pesticide aqueous formulation forms water as a dispersion medium, and the pesticide raw material (solid or oily liquid) is suspended or emulsified and dispersed in water by the action of a dispersing agent or an emulsifier and other auxiliary agents. Compared with emulsifiable concentrate, it reduces a large amount of organic solvent; compared with wettable powder, it has no dust scattering; it has low toxicity and irritation to humans and animals; it can reduce the phytotoxicity to crops; In the process of storage and transportation, it causes combustion and has high safety.
(6), microcapsule pesticide
The microcapsule pesticide is a microcapsule preparation formed by coating an active substance such as a solid or a liquid pesticide in a capsule wall material by using a microcapsule technique. The so-called microcapsule technology uses a technique in which a dispersed solid, liquid or gas is coated with a natural or synthetic polymer film-forming material to form fine particles. The film-forming material is called wall material, and the coated material is called core material. The particle size of the microcapsules is generally 1-800 micrometers. The technology separates the object from the surrounding environment through a closed or semi-permeable wall film to protect and stabilize the core material, shield the odor or color, and control the release of the core material. These functions make microencapsulation an effective commercial method in many industrial fields.
The first to introduce microcapsule pesticides to the market is Pennwalt in the United States. Its first product was microencapsulated methyl parathion introduced in 1974. Since then, the sustained release technology has received extensive attention in the pesticide industry. Every year, an "International Symposium on Controlled Release of Pesticides" was held in the United States to summarize the exchange of research results. The company subsequently introduced microencapsulated diazinon, microencapsulated permethrin, herbicides DDT, pyrethrin, chlormequat, etc., which have been microencapsulated by various wall materials. More than 50 kinds of microcapsule pesticides were commercialized in 1994.
Second, the choice of dosage form
In summary, there are many types of pesticide formulations, even in the case of aqueous formulations. Which kind of pesticide is formulated into a suitable dosage form, firstly, according to the nature of the compound, and from the needs of the target object, compare the advantages and disadvantages of various dosage forms, and also consider appropriate application methods, etc. More appropriate choices. In the determination of the dosage form, in general, a more appropriate choice can be made. In the determination of the dosage form, in general, the physical and chemical properties of the compound are key factors. A good understanding of the physical and chemical properties of the active ingredients, including the melting point, solubility, volatility, lipophilicity, hydrolysis and photochemical stability in a range of substances, is crucial for the research and development of the dosage form.
The most critical of any dosage form is to ensure its performance, to ensure that the agent is released to the target site of action and to maximize its effectiveness. The dosage form has a great influence on the quality and retention of the pesticide spray. Pesticide formulations can change their dynamic surface tension as an important parameter by the addition of auxiliaries. Therefore, the choice of auxiliaries is different, the amount of auxiliaries and the auxiliaries are different from the auxiliaries of the active ingredients. The amount of auxiliaries and the ratio of auxiliaries to active ingredients greatly affect the spray atomization of pesticides. The deposition process, which directly affects the distribution of pesticides on the surface of the plant body, especially the leaf surface and the position and droplet size of the droplets on the leaf surface; and affects the position of the active ingredient on the leaf surface and the droplet size; Retention of components, further behavior of retained precipitates, and retention from the surface of the crop to the target, further behavior of the retained precipitate, and transfer efficiency from the surface of the crop to the target; and foliar penetration of the agent and its resulting organism Activity also has a big impact.
Third, the surfactant
The surfactant can be used as a pesticide preparation which can be used as a pesticide original which cannot be directly used. As a pesticide additive, it can be applied to pesticides, which not only can improve the use of pesticides, but also reduce the amount of pesticides, reduce the impact of pesticides on the environment, and bring huge benefits to agricultural production. However, since pesticides are a kind of special chemicals with extremely strong biological activity, their control objects, protection objects and environmental conditions are very complicated. In addition to the nature and characteristics of the original drugs, the surfactants in pesticides need to be formulated. Consider the effect of the surfactant itself on the target organism.
1, solubilizer
With the micelle action of the surfactant, the solubility of the poorly soluble drug in the solvent is significantly increased, which is solubilization. A surfactant of HLB = 15-18 can be used as a solubilizing agent, but it exhibits solubilization only when the concentration of the solubilizing agent is higher than the critical micelle concentration. At this time, the poorly soluble drug is occluded or adsorbed in the oleophilic group of the solubilizing agent, and the hydrophilic group of the solubilizing agent is in the water, so that the nonpolar drug is soluble in water.
2, dispersant
The dispersant can hinder or prevent the aggregation of solid or liquid particles in the dispersion system and keep it uniformly dispersed over a long period of time. The dispersant adsorbs to the oil-water interface or the surface of the solid particles, forming a charge or steric barrier around the particles, helping to prevent the pesticide particles from re-aggregating during conditioning and storage. As the dispersing agent, generally, an anionic surfactant having a polycyclic ring such as a sodium salt of an alkylnaphthalenesulfonate and a naphthalenesulfonic acid formaldehyde condensate, a lignosulfonate or the like is used. Polymer dispersants (such as sodium carboxylate) are particularly important in the preparation of aqueous suspensions because of their adsorption properties and the ability to charge dispersed particles with a large space barrier.
3, wetting agent
Most organic synthetic drugs are sulphur-based and need to be watered. Water-based preparations such as wettable powders, suspensions, water-dispersible granules and the like are required to be added with a wetting agent. Mainly used as a wetting agent are anionic surfactants (such as fatty alcohol sulfate, dodecylbenzenesulfonate, etc.) and nonionic (such as Pingpingjia, Nongshui 100#, Nongshui 600#, spit Warm, sorbitol polyoxyethylene ether, etc.). Certain natural products such as lignosulfonate, tea dry, saponin, etc. are also preferred wetting agents. Due to the action of the wetting agent, the drug dispersion can be increased, the stability of the preparation is increased, and the release, absorption and enhancement of the drug are also facilitated.
4, emulsifier
Most pesticide crude oil or organic solutions of pesticides are incompatible with water. Emulsifiers are one of the ingredients that are indispensable for the formulation of emulsions, microemulsions, emulsions, and the like. Surfactants used as emulsifiers are mainly nonionic and anionic mixtures, such as fatty alcohol polyoxyethylene ethers or mixtures of fatty acid polyoxyethylene esters and alkyl aryl sulfonates, and many commercially available emulsifiers According to the hydrophilicity and lipophilicity of the emulsified materials, the two types of emulsifiers are mixed in a certain proportion, and the agricultural milk 2201, agricultural milk 0203B and the like are added. This type of complex emulsifier not only has good emulsifying properties, but also the emulsion prepared by it is relatively stable. It is generally believed that this is because the drug molecules are solubilized in the micelles of the anionic surfactant to cause self-emulsification, and the nonionic surfactant is adsorbed around the organic solvent particles to stabilize the formed emulsion.
Surfactants in pesticides have other special effects in addition to the effects of general surfactant solubilization, wetting, dispersion, and emulsification.
1, basic performance
The physical and chemical properties of various pesticides are quite different. The surfactants used in the formulation are also different. Not all surfactants can be used in pesticides. Surfactants as pesticide additives should have the following basic properties: firstly, suitable for the purpose of pesticide processing and application, and help to fully exert the efficacy; secondly, it is safe for crops under actual use conditions, and is harmful to humans, animals and fish. Small; secondly, the formulated preparation is stable, is not degradable during the effective storage period, and is convenient to use and safe; finally, the resources are abundant and the cost is low. Therefore, surfactants for pesticides have emerged as the times require, and often have special trade names such as Nong's Milk 700# and Nongzhu No. 2.
2, the synergy of pesticides
In general, surfactants are non-biologically active components of pesticides. However, since the pesticide is applied to the crop, the surfactant in the pesticide will have an effect on the target organism. The synergistic effect of surfactants on pesticides is a manifestation of the effective effect of surfactants on target organisms. Surfactants improve the distribution and attachment of pesticides on the surface of plants (plant leaves and worm surfaces), increase the absorption of chemicals by organisms, and even increase the transport of agents in organisms, thereby increasing the biological activity of pesticides. For example, tea saponin has a significant synergistic effect on Qiling; research by Zhenguo et al. shows that the surfactants Silwet.L77 and Sco-lil significantly reduce the surface tension of the chlorhexidine solution, thus significantly improving Its post-spray adhesion on the leaves; DucholtZ studied several surfactants for the transport and absorption of RH0007 (Hy-brex) in winter wheat plants. The results showed that in the presence of different surfactants, the leaves faced drug absorption. Increased by 0.7-1.5 times. Joel Coret et al. showed that the transport of the epidermis varied with EO values ​​by studying the interaction between C14 glyphosate and C14 chloromeron in the non-ionic surfactant-agent-plant epidermis. Surfactants with different EO values ​​can change the hydrophilicity and lipophilicity of plant epidermis. The hydrophilic or lipophilic agents can easily penetrate the plant epidermis. Liu Zhiqian et al reported that silicone surfactant can induce glyphosate fast. The ground is absorbed by plants through the pores.
3. The role of living things
Some surfactants, such as cationic surfactants, have a bactericidal action by themselves, and people have developed plant growth inhibitors, herbicides, and the like using this property. Tea saponin is an excellent nonionic surfactant and a plant insecticide. According to CN1139102A, sodium dodecylbenzenesulfonate (potassium) has a strong bacteriostatic action, and it is combined with a biologically active organic nitrogen-containing compound to obtain a biocide having a broad spectrum of bactericidal action.
Surfactants have a great effect, but not all surfactants can be used in pesticides. Because some surfactants have phytotoxic effects on crops, pesticide surfactants need to be selected according to the nature of the original drug. Also consider its impact on crop objects.
V. Precautions in the use of pesticides Summer is the season of pests and weeds of various crops, and it is also the most involved in the application of pesticides. The most used pesticides are the most prone to problems, in order to achieve safety, economy and effectiveness. Should pay attention to the following issues:
1. Buy “Reassuring Medicine†to buy “Don't buy†when you buy pesticides. First, don't buy pesticide labels or incomplete labels. Second, label “three certificates†(pesticide registration certificate, product standard number, production) The license) does not buy the medicine with incomplete label; the third is that the appearance quality is not qualified, and the fourth is that the medicine that exceeds the product quality guarantee period is not bought. Then, according to the pesticide packaging, the types of pesticides are recognized: green as herbicide, red as insecticide, black as fungicide, blue as rodenticide , and yellow as plant growth regulator.
2. Reasonable use of pesticides and pesticides to achieve six notes: First, the right medicine. There are many varieties of pesticides and different characteristics. The most suitable pesticides should be selected for the control objects; the second is the timely use of drugs. The time for medication is correct, and the control effect is ideal. If the protective fungicide must be used before or during the onset of the disease, the pre-emergence herbicide should be used before the crop is germinated; the third is to strictly control the amount of application. Any pesticide should be used according to the recommended dosage. It is easy to increase or decrease the crop phytotoxicity or affect the control effect. Fourth, the application should be even and thoughtful, and it can not be re-sprayed or leaked to ensure the safety of crops and is effective for pests and diseases; Rational mixing of pesticides, after mixing, can not increase the toxicity to humans and animals, chemical changes between the active ingredients can not occur, can not increase the cost of medication; sixth is to safely apply drugs. Dispensing and applying drugs should prevent pesticides from contaminating the skin. It is forbidden to spray high-toxic pesticides during high temperature in the summer, and the application time should not be too long. At the operation site, it is necessary to keep the liquid medicine, poisonous valleys, poisonous species, etc., to prevent poisoning of humans and animals. It should also be noted that highly toxic and highly toxic pesticides are prohibited from being used on crops such as melons, vegetables, and fruit trees to be responsible for consumer safety. In addition, pesticides must be noted for the safety of crops and the environment.
3. If there is any problem, timely treatment 1 When the drug effect is very poor or the drug is harmful, the drug should be sent to the pesticide testing unit for inspection. If it is unqualified or fake product, you can go to the industry and commerce, consumer association, technical supervision and other departments to complain or go to the court. Prosecution. 2 remedy for timely remedy, first, fertilization and remedy, the phytotoxicity of the leaves on the surface of the drug spots, leaf edge coke or plant yellowing, fertilizer can be applied to reduce the degree of phytotoxicity; second, to inhibit or interfere with plant growth Herbicide phytotoxicity can be sprayed with gibberellin to relieve; third is the phytotoxicity of some rice field herbicides, proper drainage can reduce the phytotoxicity. 3 In the event of a pesticide poisoning accident, it is necessary to take first aid measures or send it to the hospital for rescue.
6. Storage of pesticides and identification of pesticides that fail
1. Storage of pesticides
Most pesticides are organic and inorganic, and their physical and chemical properties vary from drug to drug. During the storage period, each has special requirements, which should be managed strictly according to the requirements for storage. If the storage conditions are not suitable, the pesticide will deteriorate, the efficacy will be lost, and sometimes a burning explosion or a poisoning of humans and animals will occur. Therefore, all kinds of pesticides must be properly kept in the safekeeping process. In the process of storage, pay attention to the following aspects.
(l) The houses where pesticides are stored should be as far as possible from the granary, feed room and livestock sheds to prevent pollution and mutual influence, and should not be placed together with chemical fertilizers. Because of the variety of chemical fertilizers and pesticides, the nature is different, and stored together. Chemical reactions often occur, leading to deterioration or failure. For example, when the temperature reaches 30 °C, ammonium bicarbonate will decompose, releasing ammonia gas, and ammonia gas will be synthesized into a strong alkaline ammonium hydroxide under humid conditions, so that the pesticide decomposed by alkali can reduce the efficacy.
(2) The temperature during storage should not be too high or too low. Generally, at temperatures above 30 °C, the higher the temperature, the easier the pesticide will melt, decompose, volatilize, and even burn and explode; too low temperature will have adverse effects on pesticides. For example, some liquid pesticides will freeze below 0 °C, which will reduce the efficacy. Therefore, preserving pesticides should prevent high temperatures in summer and low temperatures in winter.
(3) Some pesticides, such as wettable powders, are easy to absorb moisture, become thick or lumpy after moisture absorption, and are more troublesome to apply when they are applied. Secondly, the pesticides packaged in paper bags will be easily broken after being wet, not only bad. Handling will also pollute the surrounding environment.
(4) Pesticides are exposed to air and sunlight for a long time, which is prone to volatilization and oxidation, causing qualitative changes. Generally, solid pesticides should be packed tightly, and liquid pesticides should be packed in colored bottles or jars. Neither solid nor liquid pesticides can be exposed to direct sunlight.
More pesticide knowledge , please pay attention to China Pesticide Network
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