How to use pesticides in pollution-free vegetable production

The country is based on the people, the people are eating for the sky, the food is safe, the food is safe, and it is related to the national economy and the people's livelihood. The responsibility is more important than Mount Tai.
In the production of pollution-free vegetables, the use of pesticides has always been a "double-edged sword". How can it achieve the purpose of killing pests and germs while ensuring the safety of agricultural products? It is the focus of the majority of agricultural producers. In this issue, we invite Zhang Linhua, a senior agronomist from Jintan City Plant Protection and Quarantine Station, to introduce you comprehensively.

In order to enable the majority of vegetable farmers to learn pesticide knowledge and rational use of pesticides, and effectively control vegetable pests and diseases, it is of great significance to obtain high-quality, high-yield and pollution-free vegetables.

First, the types and properties of pesticides

1. Classified by source of raw materials

(1) Organic pesticides: These pesticides are composed of carbon compounds, mainly made of organic synthetic raw materials such as benzene, alcohols, fatty acids, organic amines, etc., so they are also called synthetic pesticides, such as trichlorfon, carbendazim, etc. . Organic pesticides can be produced industrially, with many varieties, high efficacy, wide application, low phytotoxicity, diverse processing agents and various modes of action. At present, it accounts for more than 90% of the total pesticides, and plays an important role in the development of pesticides. (2) Inorganic pesticides: mainly made of natural mineral raw materials, also known as mineral pesticides. The pesticides are characterized by stable chemical properties, are not easily decomposed, and are insoluble in organic solvents: but the variety is small, the effect is relatively simple, and phytotoxicity is apt to occur, so the use is limited. (3) Plant-based pesticides: This is a pesticide made from plants as a raw material and extracted by solvent. The active ingredient is natural organic matter, and its properties are similar to those of organic pesticides, such as pyrethrum and tobacco. Plant-based pesticides have the advantages of safety for humans and animals, no phytotoxicity to plants, and local materials. (4) Microbial pesticides; this is a pesticide made from microorganisms and their metabolites. The active substance contained is a bacterial spore, a fungal spore, a virus or an antibiotic.

Such as green worm, Beauveria bassiana, Bacillus thuringiensis, etc. These pesticides have high efficacy and strong selectivity. They do not harm natural enemies when used. They are non-toxic to humans and animals. They are safe for plants and resistant to long-term use. However, their application range is not wide enough and the effect is slow. Limitations of conditions such as seasonal and environmental factors.

2. Classification by purpose and mode of action

(l) Insecticides and acaricides: According to the route of the medicament into the body of the pest, it can be divided into a contact agent, a stomach poison, a fumigant and a systemic agent. 1 contact agent: the poisoning effect of the agent from the body wall of the pest to the body is called contact action. The agent mainly based on contact killing is called a contact agent, such as cypermethrin, phoxim, fish vine, and the like. 2 stomach poison: The agent enters the body from the digestive system of the pest and produces a poisonous effect, which is called stomach poisoning. The agent mainly based on stomach toxicity is called stomach poisoning agent, such as trichlorfon and insecticidal double. 3 fumigant: The agent is in an aerosol state, and the poisonous effect of the pest's respiratory system enters the body. Such as aluminum phosphide, zinc phosphide, and the like. Both can release phosphine gas to kill pests. 4 systemic agent: the agent applied to the stems or roots of plants, which is absorbed by plants and transported throughout the plant, and the pests feed on plants and thus produce toxic effects. Such as monocrotophos, dimethoate and so on.
(2) Ovipositant: An agent that prevents the development of embryos in the egg and prevents the larvae or mites from hatching, such as Park Yuling and Amitraz.
(3) Fungicide: According to the role of chemical sterilization, it can be divided into the following three main types. 1 protectant; spray the agent on the surface of the plant before the plant is susceptible to disease to kill or prevent the infection of the plant by pathogens or pathogens. Most of the fungicides currently used are protective agents, such as Bordeaux mixture, zinc, chlorothalonil, and sulfuric acid preparations. Such agents are often less effective when used after the onset of the plant. 2 therapeutic agents: agents that have therapeutic effects on diseases, such as retort, thiram, and the like. Treatment of the drug for the disease is much more difficult than protection of the drug. This is because after the invasion of the bacteria, it is closely related to the plant, which enhances the resistance of the bacteria to the agent. It usually kills the dose of immersed bacteria, and often causes phytotoxicity to plants. Therefore, the current application of therapeutic agents is far less extensive than protective agents. Use a therapeutic drug only if it is unavoidable. 3 Systemic agents: Agents that are absorbed by plants' leaves, stems, and roots, enter the plant and can metabolize, retain, or produce metabolites in the body to protect plants from pathogens or to treat plant diseases. Such as rust sodium, carbendazim, diclosan and so on. Since the advent of systemic agents, it has played a prominent role in the prevention and control of plant diseases, but there are also problems that pathogens are susceptible to such agents. Therefore, in recent years, people have attached great importance to making a mixture or a mixture of a protective agent and a systemic agent. In addition to the above-mentioned types of drugs, there are also acaricides, nematicides, rodenticides, herbicides, plant growth regulators, etc.

1. Priority selection of biological pesticides

Bio-insecticides and acaricides commonly used in production: Bt, avermectin, Liuyangmycin, huaguangmycin, anisidine, rotenone, matrine, cucurbitine, etc.; fungicides: Jinggangmycin, Chunlei Taxomycin, polymycin, Wuyolin, agricultural streptomycin, etc.

2. Reasonable selection of chemical pesticides It is strictly forbidden to use highly toxic, high-toxic, high-residue, high-bio-rich, high-grade (teratogenic, carcinogenic, mutagenic) pesticides and their compound preparations. Such as methamidophos, carbofuran, 1605, 3911, omethoate, insecticidal mites, chlorpyrifos, hexachlorocyclohexane, DDT, methylisophosphorus, aldicarb, methomyl, zinc phosphide, long-lasting effect Phosphorus, organic mercury preparations, etc. Some pesticide residues are large, such as dicofol, and its components are slowly decomposed. There is still residue in the crop after one year of application, and it is not suitable for use on vegetables.

The second is to choose high-efficiency, low-toxic, low-residue chemical pesticides. The production of pollution-free vegetables allows the use of limited chemical pesticides. The quality of toxic residues in vegetables does not exceed the national sanitary standards, and the metabolites in the human body are harmless, easy to remove from the human body, and have little lethal effect on natural enemies. . The chemical insecticides and acaricides used are limited to trichlorfon, phoxim, dichlorvos, risperid, cypermethrin, deltamethrin, fenvalerate, ketone, diamethym, nisol, and蚜 fog, 太太保, chlorfenapyr, diflubenzuron, buprofezin and so on. Limited chemical fungicides: Bordeaux mixture, DT, killable, carbendazim, chlorothalonil, methyl thiophanate, dexamethasone, ethyl phosphine aluminum, metalaxyl, trisodium phosphate, etc.

Third, the use of pesticides

1. The right medicine should be based on the full understanding of the performance and use of pesticides; according to the types of pests and diseases, use appropriate pesticide types or dosage forms. For example, the stomach poison in the insecticide is effective in controlling the chewing mouth pests, and the pest control is ineffective; the buprofezin (Popular) has special effects on the whitefly nymph, and is ineffective against the aphids; There are special effects, but the effect of preventing and treating melon is poor; metalaxyl is effective against various vegetable downy mildew, early blight, late blight, etc., but it is not effective against powdery mildew. In the prevention and control of pests and diseases in protected areas, different dosage forms of pesticides can be flexibly selected according to weather conditions. Sprays such as powders, wettable powders and suspensions can be used on sunny days. Tobacco sprays, dust sprays or smoked smoke should be used on cloudy days. Room humidity, reducing leaf dew and leaf edge spitting, has obvious effects on controlling low temperature and high humidity diseases.

2. Appropriate use of drugs According to the law of occurrence of pests and diseases, strictly control the best prevention and treatment period, and make timely use of drugs. For example, before planting or planting vegetables, measures such as greenhouse application, soil treatment and chemical dressing should be adopted; when aphids, moths, and low density of whitefly occur, local application is used. Different pesticides have different properties, and the control period is different. Biological pesticides have a slower effect and should be used 2 to 3 days earlier than chemical pesticides.

3. Scientific use of drugs should pay attention to alternate rotation of pesticides using different mechanisms of action, can not be singularized for a long time, to prevent the emergence of resistance to pathogenic bacteria or pests, and to maintain the control effect and service life of the medicament. In the early stage of vegetable growth, high-efficiency and low-toxic chemical pesticides and biological pesticides were mixed or alternately used, and bio-pesticides were mainly used in the late growth stage. The use of pesticides should promote low-volume spray methods and pay attention to uniform spraying.

4. Select the correct spraying point or site to determine the different parts of the plant as the target according to the characteristics of different pests and diseases in different periods, and carry out targeted application. To achieve the purpose of timely controlling the occurrence of pests and diseases, reducing the number of pathogens and reducing the number of insects, thereby reducing the use of drugs. For example, late blight usually occurs first on the front (south) crop of the shed, so it should be sprayed on the front crop in time. The occurrence of downy mildew is initiated by the lower leaves. The early control of downy mildew is focused on the lower leaves, which can alleviate the upper leaves. Insects such as aphids and whitefly are easy to inhabit the back of young leaves, so they must be evenly sprayed, with the nozzles facing up and the back of the sprayed leaves.

5. Reasonable compounding agent adopts mixed medicine method, which can achieve the purpose of controlling multiple pests and diseases by one application, but the pesticide compounding should maintain the original active ingredient or have synergistic effect, and does not increase the toxicity to humans and animals. Good physical properties are prerequisites. Generally, neutral pesticides can be mixed; neutral pesticides and acidic pesticides can be mixed; acidic pesticides can be mixed; alkaline pesticides can not be mixed with other pesticides; microbial pesticides (such as Bt) cannot be combined with fungicides and Mixing strong pesticides; mixed pesticides should be used with mixing. When using various biological pesticides mixed with chemical pesticides, the chemical pesticides to be mixed can only be chemical pesticides that are allowed to be used.

6. Do not arbitrarily increase the amount of drugs and the number of sprays. The safe use guidelines for pesticides and the production standards for pollution-free vegetables stipulate that each pesticide is used in different vegetables.

The amount of drug used, the number of drugs used, the maximum allowable residue and the safe interval must be strictly enforced in the production of pollution-free vegetables. It is necessary to completely change the lagging habits of increasing the amount of drugs and the number of spraying, and the confusion of various pesticides. . The safety interval of pyrethroid pesticides is 5-7 days, the organophosphorus pesticides are 7 to 14 days, the fungicides are chlorothalonil, Daisen zinc, carbendazim for more than 14 days, and the remaining 7 to 10 days. Pesticide blends perform a safe interval between the most residual active ingredients. After the vegetable spray, the pesticide must be degraded to no residual toxicity before it can be harvested. Vegetables that have been picked many times must be harvested after harvesting to ensure the health of consumers.

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