Common problems in the selection, purchase and use of pesticides

Pesticides refer to chemicals used to prevent, eliminate or control diseases, insects, weeds and other pests that harm agriculture and forestry, and to purposefully regulate the growth of plants and insects, or a mixture of biological or other natural substances and their preparations. Qualified pesticide products must have "three certificates". Pesticide "three certificates" refer to pesticide production certificate, pesticide standard and pesticide registration certificate. The "three certificates" are issued on the basis of products, that is, each pesticide product, produced by different manufacturers of the same pesticide product, has its own "three certificates".

The meaning of fake pesticides and inferior pesticides

1. The name of the active ingredient does not match the approved label

2. Impersonate non-pesticides as pesticides or other pesticides as pesticides

3. Counterfeiting, forging or transferring pesticide registration certificates or pesticide labels

4. The State officially announces the prohibition of the production or cancellation of registered pesticides (because they can no longer be used as pesticides).

In any of the following cases, it is an inferior pesticide:

(1) the product quality is seriously inconsistent with the requirements of pesticide product standards.

(2) exceeding the quality guarantee period and losing its use value; or using it for a limited time without indicating the expiration time

(3) mixed with harmful ingredients that can cause drug damage or other losses

(4) the packaging or label is seriously damaged.

Shelf life of pesticides

The period between the date of factory production and packaging and the final date of no degradation of quality and efficiency of pesticide products is called shelf life. During the shelf life, the quality of pesticide products should not be lower than the technical index values stipulated in the quality standards, and users should apply according to the control object, application method, concentration (or dose) on the pesticide label, satisfactory control effect should be achieved without drug damage.

Reasons for the change of Pesticide quality during Storage and Transportation

Chemical pesticides are chemicals synthesized by chemical reactions of two or more substances under certain conditions.

Since pesticides are chemical substances, of course, they are also affected by external light, heat, humidity and other natural factors, resulting in changes in the original performance, and even deterioration and failure. There are many factors leading to changes in pesticide quality during storage and transportation, mainly as follows:

1. Temperature. The higher the temperature, the greater the effect on the quality of pesticides. In addition, the temperature below zero also has an impact on the quality of pesticides, especially liquid pesticides, which are prone to crystallization or precipitation, reduce emulsifying power and reduce efficacy.

2. Humidity. Too much humidity in the air will cause changes in the quality of pesticides and affect their efficacy. Especially after the powder or wettable powder pesticide absorbs the water in the air, it is easy to make the powder particles agglomerate or agglomerate, reduce the powder fluidity or the emulsion suspension rate of wettable powder, so as to reduce the control effect.

3. Light. Light is also a very important factor leading to the deterioration and inefficiency of pesticides, which can promote the photochemical reaction of the effective components in pesticides and decompose them.

4. Quality of raw materials. The quality of raw materials is high, the content of pesticides produced is also high; the quality of raw materials is low, not only the effective components of the finished products are low, but also produce a lot of impurities, increasing the toxicity of pesticides to humans and animals. This is most obvious in the synthesis of organophosphorus pesticides.

5. Pesticide packaging. In particular, EC pesticides should be tightly sealed. If the packaging is not tight and not intact, it is easy to cause moisture absorption, decomposition and volatilization of the product, and it is easy to come into contact with air oxidation and decomposition to cause quality change. This is the case with omethoate.

According to some physical and chemical properties of pesticides, not only temperature, humidity, sunlight, air and pressure have effects on the quality of pesticides, but also acids and bases have great effects on the quality of pesticides. Therefore, most pesticides can not come into contact with acid or alkaline substances during storage.

Pesticides cannot be stored in the same warehouse as chemical fertilizers.

If there are more varieties of chemical fertilizers, there will be more varieties of pesticides, and their properties are different. For example, chemical fertilizers are volatile, explosive, acidic and alkaline. Pesticides are also decomposable, flammable, explosive and toxic. So you can't store it in the same library.

Distinguish the quality of pesticides and buy pesticides scientifically

1. Powder

(1) appearance. The appearance of the powder should be loose fine powder, no lumps.

(2) hygroscopicity. Before taking the powder to test the hygroscopicity, first check whether there is any moisture outside the powder packaging paper bag, if so, of course it is a sign of high hygroscopicity. Then take a little powder from the bag and pour it on a piece of white paper, pick up the white paper and pinch it on the outside of the paper with your thumb and forefinger. If it is glued together, it shows that the powder has absorbed moisture, and if it is used for spraying powder, it indicates that it is of poor quality; if it is still a loose fine powder, it shows that it is a good powder spray. The hygroscopicity of wettable powder is higher than that of ordinary powder, but this agent is used with water anyway, and the effect of hygroscopicity on it is less than that of powder spraying. However, moisture absorption is not always a good thing, because pesticides are easy to deteriorate when they are wet.

2. Wettable powder

(1) appearance. Should be a very fine loose powder, no lumps.

(2) wettability. Use a large glass bottle filled with water, then gently pour a spoonful of wettable powder from the top on the surface of the water with a small spoon. After 2 minutes, if it can be completely soaked and gradually sink, it is a wettable powder with good wettability; if the powder is still floating on the water, it is a potion with poor wettability. In this way, we can also distinguish which kind of wettable powder is the wettable powder, which is the powder for spreading powder, and what is easy to wet is the wettable powder. General powders are not wetted.

(3) suspension. Plug the top of the glass bottle that has been tested for wettability, shake it back and forth 30 times, then leave it for 10 minutes and have a look. If the liquid is still turbid and the powder settles at the bottom of the bottle is not long, it is a wettable powder with good suspensibility; if more than half of the powder has settled or the solution has been nearly clarified, the suspension performance is not good; if all the powder has sunk to the bottom of the bottle, it is a wettable powder with poor suspensibility; if the agent is agglomerated, it is not a good wettable powder.

3. EC

(1) appearance. First see if the EC in the medicine bottle has been delaminated, and then see if it is turbid and crystallized. Any EC that is not delaminated, turbid and uncrystallized is a good EC. The EC with delamination, turbidity or crystallization has gone bad, and its efficacy is poor when used. Of course, if the EC is put at a very cold temperature and crystals are found, and it can be dissolved at room temperature, it cannot be considered as deteriorating.

(2) emulsification. Pour a volume of EC into 19 parts of water, mix and shake for 30 times, then rest for half an hour to see if there is any oil or paste floating on the surface, and then see if there is any sediment at the bottom. If none, it shows that the emulsifying power of the agent is very good. When measuring emulsification, if the EC put in the water can spread quickly and turn white is the best EC, which can be diffused without stirring itself, which is also called the emulsion with strong diffusivity; if there is obvious precipitate, or there is an oil slick on the water, the cream is the EC with poor emulsifying performance.

4. Suspending agent. Suspending agent should be slightly viscous, flowable suspension, its viscosity is very small, uniform. If delamination occurs due to long-term storage, and the uniform state can be restored by shaking, it can still be regarded as a qualified product. If it can not be re-transformed into a uniform suspension, the sediment at the bottom cannot be shaken, and the suspension performance is not good.

Problems needing attention in the mixed use of pesticides

1. The purpose of mixed use of pesticides should be made clear, and should not be mixed for mixed use. The mixed use of pesticides should achieve the purpose of increasing efficiency, treating both sides and expanding the scope of prevention and control. If the above purpose cannot be achieved, it should not be mixed. Otherwise, it will cause waste, fail to achieve the desired effect, and even cause drug damage.

2. Adverse chemical and physical changes should not occur after pesticide mixing. If the medicament is not decomposed after mixing, the EC is not destroyed, and the suspension does not produce flocculation or a large amount of precipitation, it can be mixed.

3. The mixed liquid (powder) should not cause drug damage to crops. If there is drug damage, it can not be mixed with each other.

4. After mixing, the efficacy of the mixture should be improved, or at least it should not be reduced, that is to say, it should increase the efficiency after mixing.

5. After the chemicals are mixed, the acute toxicity of the mixture is generally not higher than their original toxicity, that is to say, it can not be increased.

The cause of drug damage

1. Misuse it on sensitive crops. Most pesticides have their corresponding sensitive crops, which should be strictly prevented from misuse.

2. Use drugs in the sensitive stage of crops. The resistance of crops to pesticides is different in different growth stages. generally speaking, the resistance of seeds is the strongest, and most crops are prone to drug damage at seedling stage and flowering stage. Gramineae crops are more sensitive to pesticides at booting stage and less sensitive to pesticides from tillering stage to booting stage.

3. High temperature, high humidity and strong sunshine are easy to cause drug damage. For example, stone-sulfur mixture is easy to cause drug damage when used in high temperature weather above 32 ℃. There are also a few agents that are easy to cause drug damage when used at low temperature.

4. Excessive dosage, high concentration or improper application method. There is a limit to the tolerance of crops to pesticides, if the dosage or concentration is too high, it will cause drug damage to crops.

5. Inappropriate mixed use. Each pesticide has a certain combining ability, and the wrong mixed use often causes drug damage.

Main symptoms of drug damage to crops

1. Spots

Spot damage mainly occurs on leaves and sometimes on stems or fruit epidermis. The common ones are brown spot, macula, withered spot, reticular spot and so on. The drug spot is different from the spot of physiological disease, the distribution of drug spot on the plant is irregular, and the occurrence of the whole plot is light and severe. Disease spots are usually common, and the locations of plant symptoms are consistent. The spots of drug spots are also different from those of fungal diseases, the size and shape of drug spots change greatly, and the disease spots have the same disease center and spot shape.

2. Etiolation

Yellowing can occur in the stems and leaves of the plant, especially in the leaves. The main reason for yellowing is that pesticides hinder the normal photosynthesis of chlorophyll. Mild occurrence showed yellowing of leaves, while severe occurrence showed yellowing of the whole plant. Leaf yellowing can be divided into heart leaf yellowing and basal leaf yellowing. The yellowing caused by drug damage is different from that caused by the lack of nutrient elements. the former often changes from yellow leaves to withered leaves, with more sunny days, faster yellowing, more overcast and rainy days, and slow yellowing. The latter is often related to soil fertility, and the performance of yellow seedlings in the whole plot is consistent. Compared with the yellowing caused by virus, the yellow leaves of the latter often show broken green, and the diseased plants show systematic symptoms, and the diseased plants are mixed with healthy plants in the field.

3. Deformity

The deformities caused by drug damage can occur in the stems, leaves and roots of crops, such as rolled leaves, clumps, swollen roots, deformed ears, deformed fruits and so on. Drug damage malformations are different from virus disease deformities, the former is common, showing local symptoms on the plant, while the latter is often sporadic, showing systemic symptoms, often mixed with broken green veins, wrinkled leaves and other symptoms.

4. Wilt

Drug-induced wilt often shows symptoms in the whole plant, which is mostly caused by herbicides. The symptoms of wilt caused by drug injury are different from those caused by plant disease. the former has no disease center, and most of the occurrence process is slow, first yellowing, then dead seedlings, and no browning of rhizome conducting tissues, while the latter is mostly blocked by rhizome conducting tissues. when sunlight exposure, evaporation is large, wilting first, then chlorosis dead seedlings, root duct often browning.

5. Growth stagnation

This kind of drug damage inhibits the normal growth of crops and makes the plant grow slowly. Herbicide damage generally has this phenomenon, but it is more or less different. The slow growth caused by drug damage is compared with the stiffness and deficiency of physiological diseases, the former is often accompanied by drug contact or other drug damage symptoms, while the latter is characterized by poor root growth, while the stiffness caused by deficiency is characterized by yellowing or dark green leaf color.

6. Infertility

Infertility is a reflection of drug damage caused by improper use of drugs in the reproductive period of crops. Drug-induced infertility is different from climate-induced infertility, the former is whole-plant infertility, sometimes partially fruiting, but mixed with other drug-harmful symptoms, while climate-induced infertility has no other symptoms, and the phenomenon of whole-plant infertility is rare.

7. Shedding

This kind of drug damage is mostly shown in fruit trees and some dicotyledonous plants, with symptoms such as falling leaves, falling flowers, falling fruits and so on. Attention should be paid to the difference between fallen leaves, flowers and fruits caused by drug damage and those caused by atmospheric or cultivation factors, the former is often accompanied by other drug damage symptoms, such as yellowing, scorching, and then falling leaves. The latter is often related to disastrous weather, which often occurs in strong winds, torrential rains and high temperatures. If the cultivation factors are short of fertilizer or grow too much, it will cause falling flowers and fruits.

8. Bad fruit

This kind of drug damage is shown on the fruit of the plant, which makes the size of the fruit smaller, the fruit surface abnormal, the quality worse, and affects the edible value. The bad fruit caused by drug damage is different from the bad fruit caused by disease, the former has only disease symptoms, no symptoms, and sometimes accompanied by other drug damage symptoms; the latter has disease symptoms and many symptoms, and some viral diseases show systemic symptoms or no other symptoms.

Matters needing attention in purchasing pesticides

1. Look at the product introduction. Fake and shoddy pesticides are often blurred, different and wrong words, unscientific exaggerated efficacy, incomplete content and so on.

2. Look at the registered trademark. First, there is the word "registered trademark", and the other is "trademark pattern", both of which are indispensable. Counterfeit pesticides often have no trademark or trademark pattern.

3. Look at two certificates and one. The two certificates refer to the Pesticide Registration Certificate, the production license or the quasi-production Certificate. No. 1 refers to "product standard code". You can rest assured to buy pesticides with two certificates and one complete number on the label.

4. Look at the expiration date and production batch number. The "period of validity" is the maximum period of validity of the pesticide calculated from the production package. The "production batch number" is the batch number of the year, month, day and day of the pesticide production. Pesticides beyond their expiration date cannot be purchased.

5. look at the name and location of the factory. The factory name and address of the enterprises that formally produce pesticides are clear, and some manufacturers also have postal codes, telephone numbers and telegram registrations. Fake and shoddy pesticides cannot be clearly marked on the label.

6. See if there are two certificates and validity period for imported repackaged pesticides. If so, you can rest assured to buy.

7. Look at the appearance quality. The main purpose is to check whether there are agglomeration, stratification, precipitation and leakage of pesticides. If there is one of these phenomena, it is an expired or substandard pesticide, it is best not to buy it.

8. See whether the business unit is formal. When buying pesticides, be sure to check whether the operator has a business license and a pesticide license. It is recommended that you go to the well-documented agricultural technology department to buy pesticides, they can also guide you when to use the most appropriate, which medicine is the most effective.

Problems that should be paid attention to when using pesticides

1, prescribe the right medicine to the case, there are many kinds of pesticides with different characteristics, so the most suitable pesticide should be selected according to the object of prevention and control.

2. The control effect is ideal only when the medicine is used at the right time.

3. Strictly control the amount of pesticide application and use it according to the recommended dosage. It is easy to cause crop drug damage or affect the control effect.

4. the application should be uniform and should not be re-sprayed or missed, so as to ensure the safety of crops and effective control of diseases, insects and rodents.

5. The reasonable mixed use of pesticides can not increase the toxicity to humans and animals, the chemical reaction between the effective components can not occur, and the drug cost can not be increased.

6. it is necessary to apply and dispense drugs safely so as to prevent human and animal poisoning.

7. Highly toxic and highly toxic pesticides are prohibited to be used in melons and fruits, vegetables, fruit trees, traditional Chinese medicine and other crops.

Five substitutes for prohibited pesticides in vegetable production

Vegetable production "pollution-free" has been the trend of the times, the majority of vegetable farmers have a deep understanding of this. However, five kinds of highly toxic and high residual pesticides, such as methamidophos, which have been used by vegetable farmers for a long time, have been banned in the technical regulations for the production of pollution-free vegetables. In this paper, five kinds of substitute pesticides with banned pesticides are introduced to achieve the same control effect.

1. Methamidophos. It is a broad-spectrum insecticide, which used to be used to kill all kinds of pests, but it is highly toxic and has a residual period of more than 30 days. It often causes human and animal poisoning and is the primary prohibition of pesticides in the production of pollution-free vegetables. Attention should be paid to:

(1) for Lepidoptera pests such as Pieris rapae, Plutella xylostella and Chilo suppressalis. There are two kinds of alternative pesticides: one is biological pesticides, such as moth fly quick kill, century kill, Taoxiaoling, Nongdi Le, etc., and the other is the use of compound pesticides, which are often mixed with dichlorvos.

+ BT, dichlorvos + kung fu, etc. In use, attention should be paid to: ① spray control of pests in the young age, the effect is good; ② rotates the use of all kinds of pesticides, more use of biological pesticides, so as to prevent pests from producing drug resistance; ③ pesticides now have contact effect, should choose the best effect of spraying when pests find food, such as pod borer mostly climb out of the pods in the morning to find food, at this time spray insecticide effect is the best.

(2) for migratory pests such as yellow ladle jumping beetle, Huang Shougua and so on. The alternative pesticides are dichlorvos, agricultural delight, phoxim and so on. In use, it should be noted that the control effect of ① is good in a large area at the same time; when the number of ② is large, besides spraying, root irrigation should also be used to kill underground larvae; ③ should be controlled continuously for 3 times at an interval of 5 min for 7 days.

(3) aphids and whitefly pests. It is easy to kill, so it can be controlled in time with aphids, dichlorvos and other agents.

2. Dicofol. In the past, it was mainly used to kill red spiders and mites. The substitute pesticides are Chongmike, Chongmijing, Aifuding and so on, and the effect is obvious.

3. Omethoate. In the past, it was mainly used to kill the thrips of melons, and the substitute pesticides were lice aphid, dimethoate and so on.

4. Carbofuran. In the past, it was mainly applied to soil to kill nematodes and other soil pests. The alternative pesticides are Milol, dimethazone and so on. In addition, the same effect can be achieved by using methods such as turning the soil and applying lime.

5. Methyl 1605. In the past, it was widely used to kill all kinds of vegetable pests, such as Spodoptera litura, alternative pesticides and methods similar to methamidophos.

Vegetable production should strictly abide by the pollution-free operation rules, prohibit high toxic and high residual pesticides, and strictly abide by the safety period regulations for pesticides that are allowed to be used. By improving the technical level of pesticide application, we can not only meet the standard requirements of pollution-free vegetables, but also achieve the goal of high yield and high quality.