Someone says that the pesticides in your farm shop don't work, you can tell him like this--

Daily agricultural materials

People often say that pesticides don't work! But the question comes, whether the product is good or not also has something to do with many other reasons. This article has probably explained all the reasons. I would like to share it with you cat friends.

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1. Factors related to pharmacy

Chemical composition of pharmaceuticals

For example:

① organochlorine insecticides have poor effect on mites, but have high effect on Lepidoptera pests.

② chlordimeform has a good effect on Lepidoptera larvae and mites.

③ has significant control effect on wheat aphid, but has almost no effect on APHIS gossypii.

Physical and chemical properties of pharmaceuticals

The solubility, wettability, spreadability, dispersibility and stability of the agent all affect the efficacy of the drug. In order to improve the deposition, wettability and wettability of the solution, surfactants or oils must be added to the solution to reduce the surface tension and improve the adhesion of the solution.

The mode of action of the drug

For example:

① phenoxy carboxylic acid herbicides such as 2mae 4murD, 2je 4-butyl ester and 2methyl 4Cl are effective on broad-leaved weeds but not on monocotyledons.

It is used to control annual and perennial broad-leaved weeds and sedges in cereal crops, and can promote growth at low concentrations and inhibit growth at high concentrations (hormonal herbicides)

② internal inhalation insecticides are effective against piercing mouthparts pests, while stomach poisons are effective against chewing mouthparts pests, but almost ineffective against piercing mouthparts pests.

The contact insecticide is effective against both kinds of pests.

Concentration / dose of the agent

When ① is generally used, the efficacy will be improved with the increase of drug concentration, but beyond a certain limit, the efficacy may not be improved with the increase of concentration.

For example:

For example, phenoxy carboxylic acid herbicides belong to internally absorptive conductive herbicides, if the dosage is too large, the plant transport tissue will be killed, and the drug can not be transmitted to the root system or growth point, but the efficacy is not good.

② insects have a strong sense of taste. If the content of insecticide in food is too high, some insects will have antifeedant effect immediately.

If the dosage of ③ is too much, it will cause loss and can not improve the efficacy, and it is easy to cause drug damage to plants, promote the rapid development of drug resistance of pests, kill natural enemies, pollute the environment and so on.

two。 Factors related to the object of prevention and control

Feeding mechanism of insects

① pests must come into contact with crops no matter they are active or feeding, so the contact insecticides are most widely used.

In terms of pest activity habits, it can be divided into "foliar pests", "latent herbivorous pests (such as citrus leaf moth)" and "borer pests". The insecticides with contact effect can only be used to control "borer pests" before the pests get into the crops; the insecticides with internal suction / infiltration effect are suitable for the control of "borer pests" and "latent predators" that have been drilled into the crops.

As far as the feeding mode of pests is concerned, it can be divided into "chewing organ pests" and "piercing mouthparts pests". The insecticides with contact / stomach toxicity are suitable for the control of "chewing organ pests"; the insecticides with internal suction / infiltration are suitable for the control of "piercing mouthparts pests".

② stomach poisons such as trichlorfon, diflubenzuron, etc. are sprayed on the leaves, stems and fruits of crops, or made into poison baits that pests like to eat, or poisonous valleys are spread in crop fields. They are very effective against chewable mouthparts pests such as armyworm, locusts, mole crickets, ground tigers, etc., but not against piercing mouthparts pests.

③ internal inhalation insecticides such as methamidophos and carbofuran are highly effective against piercing mouthparts pests such as aphids, mites and scale, and are easy to use, may not necessarily be well sprayed, and can be used for seed treatment and soil root application.

The developmental stage of the physiological state of the control object

In the whole life cycle of ①, the resistance of larva and adult stage is poor, the egg is the strongest, and the larva is the most serious period, so the larval stage should be selected for control.

The drug resistance of different instar larvae of ② is also different, the drug resistance of low instar larvae is poor, the drug resistance of old instar larvae is strong, and the control effect is high before the third instar. 5 days after the peak of egg hatching is the best period for prevention and treatment.

③ should also pay attention to the physiological state of bacteria in disease control, winter spores have strong drug resistance, when spores germinate, the drug resistance of young germ tube decreases, and the control effect is good; when bud tube invades plant growth and reproduction, pesticide application is ineffective, so it is best to control plant diseases in the early stage of disease.

Timely application of weeds in the field of ④ crops is also an important aspect to ensure the control effect: on the one hand, the application period should be determined according to the nature, characteristics and biological characteristics of weeds, and the sensitivity of crops should also be taken into account.

Generally speaking--

A: for annual weeds, they should be applied at the budding stage, and at the latest at the 3-Mel-5-leaf stage. After the weeds grow up, in addition to their own damage, the resistance to herbicides is enhanced, so it is difficult to achieve the purpose of selective elimination.

B: for perennial weeds, it is necessary to make them grow to a certain leaf area before they can be applied, so that the weeds can reach an effective dose and cause poisoning and death, but this kind of weeds should be applied before flowering at the latest.

As soon as the weeds enter the flowering stage, that is, from vegetative growth to reproductive growth, the organ differentiation and physiological and biochemical reactions of weeds are changed, so that herbicides can not play their due role.

C: for broadleaf weeds, soil treatment should be used to control broadleaf weeds at budding stage, or after reaching a certain leaf area, morphological selection, position difference selection, biochemical selection or directional spraying should be used to control broadleaf weeds, and the application time should be when the weeds are in a tender state. And the crop is in the period of high resistance.

Surface structure and performance of prevention and control object

① plants have hairs or thick waxy layer on the surface, and the leaves are upright, and the general solution is not easy to deposit, such as Monocotyledons; dicotyledons are spreading, less hairs, thin waxy layer, chemicals are easy to deposit.

The wettability of ② varies greatly among different kinds of insects, the insects with thin wax layer, few secretions and no scales are easy to be wetted and deposited, while the insects with thick wax layer, more secretions and more scales are not easy to be wetted and deposited.

The physiological water absorption of leaves (roots) of ③ plants also has a great influence on the absorption of drug solution.

For example, the physiological water absorption is the strongest in the evening or early morning, especially in the evening, and the absorption of pesticides is also the highest for internal absorption pesticides.

3. Environment-related factors

The change of environmental conditions, on the one hand, affects the physiological activities of organisms, on the other hand, it will affect the physical and chemical properties of agents and lead to the effect of drugs. The main environmental factors are temperature, humidity, Rain Water, light, wind and soil properties.

Temperature

① temperature has a great influence on the efficacy of pesticides, especially insecticides.

Temperature coefficient of pesticides: the ratio of the median lethal dose (LD50) of a pesticide to a test insect at 20 ℃ to the LD50 at 30 ℃.

② positive temperature coefficient type

That is, in a certain range, the temperature is high and the efficacy is good. Most of the insecticides used at present belong to the type of positive temperature coefficient, and the change of temperature has a great influence on the efficacy of trichlorfon against Dendrolimus punctatus, for example, the efficacy of trichlorfon against Dendrolimus punctatus under 20 ℃ is 4 times higher than that under 10 ℃, and the control effect of dimethoate below 15 ℃ is very poor.

③ negative temperature coefficient type

That is to say, in a certain range, the temperature is low and the efficacy is good. There are not many insecticides belonging to negative temperature coefficient type, mainly in DDT, pyrethroids and synthetic pyrethroids such as pyrethroids.

Generally speaking, ④ shows high biological activity, strong penetration and rapid penetration at higher temperature.

High temperature can also reduce the surface tension of the object and increase the distribution performance of the liquid; under the condition of high temperature, the pest has high respiratory intensity, exuberant metabolism and strong activity, which are conducive to the killing effect of the drug. However, the application of pesticides at high temperature will also increase the damage to crops and the chance of poisoning to humans and animals.

Humidity

① humidity has little effect on the control effect of the insecticide, but it is very complex.

Generally speaking, high humidity can accelerate the hydrolysis of some agents, resulting in drug failure or drug damage, especially the powder is easy to accumulate or agglomerate and affect the efficacy and produce drug damage.

The rain will wash away the medicament, so it should be sprayed in time after the rain.

② for EC, wettable powder and other dosage forms

After the spray agent is dried, high humidity or dew helps the agent to disperse and spread again, which is beneficial to the exertion of the efficacy.

The humidity requirement range of ③ insecticide is low.

Generally speaking, under the condition of high temperature, low humidity, low temperature and high humidity, that is, spraying from 4 pm to evening, the control effect is good in the evening or evening.

Most areas of Northwest China belong to this kind of climate in summer and early autumn, so the above-mentioned time rule of drug use can be used in production.

For fungicides, ④ has a positive correlation between humidity and efficacy in a certain range.

When the humidity is high, the protective fungicide is easy to kill the bacteria that invade and infect; when the soil is treated, the high humidity is also easy to make the fungicide exert its efficacy. However, if the humidity is too high, it is not conducive to the internal absorption, penetration and transport of internal absorbent fungicides.

The application of herbicides is mainly soil treatment, so the relationship between humidity and efficacy is very close, in a certain range, the greater the humidity, the better the effect, while the foliar treatment is the same as pesticides and fungicides.

Light

There is a close relationship between light and temperature, and the effect of temperature on efficacy has been described. as far as light is concerned, the reflection of different agents is also different.

Most of the pesticides in ① can be decomposed by light to varying degrees, and some of them will even be degraded quickly under light and become ineffective.

For example, phoxim can be photolyzed more than 1/2 in 4 hours under light, so it can only be used in soil treatment to control underground pests, but if sprayed in the evening, it can exert a strong effect in nearly 20 hours. Nicotine against aphids and other pests should only be applied in the evening. Pyrethrin can only be used to control indoor sanitary pests and storage pests because of its easy photolysis.

However, because of their easy photolysis, these agents have the advantages of short residual period and low residual toxicity, so they have become advantages in not polluting the environment, protecting natural enemies, pollution-free and so on.

The ② herbicide trifluralin is easily photodegraded and needs to be raked into the soil immediately after application.

On the contrary, many agents have better efficacy in light, such as parathion to control insects, the effect is better under light, so it can be sprayed on crops such as in the morning after the dew goes down.

In particular, many herbicides (mainly photosynthesis inhibitors, such as substituted urea, trioxobenzene, etc.) have better effects under light. As an actinic herbicide, herbicide can kill weeds only under light.

Wind

Wind affects the progress of pesticide application, mainly on spraying method and powder spraying method. When spraying pesticides routinely, it is not suitable if the wind force exceeds level 3.

First of all, ① wind can cause drift loss of powder or liquid, and then affect the uniformity because the particles are concentrated in one wind direction, which indirectly affects the control effect of the drug.

In addition, spraying in windy conditions is also easy to cause poisoning by operators or damage caused by blowing the medicine on sensitive crops in nearby plots.

If dichlorvos is sprayed in the cotton field, if sorghum is planted within 5-m downwind, it is in danger of causing drug damage; spraying herbicides such as 2meme 4-D in the wheat field is easy to cause drug damage in the vicinity of Chinese wolfberry.

② low-volume and ultra-low-capacity spray must rely on a certain amount of wind to operate normally, and the motorized fog sprayer can only rely on the wind generated by itself to send out the particles and blow them to the crops.

Rain

Rain generally has an effect on the efficacy of stem and leaf treatment agents, and the degree of influence is related to the type and nature of the agents, the time from rain after application and the amount of rainfall.

① internal absorbent can be absorbed by plants within a certain period of time after use, then the effect of rainfall on its efficacy is smaller.

If Najiaojing is a highly selective internal suction type stem and leaf treatment agent, there is no effect on the efficacy in case of rainfall 3 hours after spraying; contact poison, stomach poison and powder spraying are generally ineffective after rain, so re-spraying should be considered.

The rainfall adapted to ② can significantly improve the control effect of pesticides used in soil treatment.

Especially for herbicides, the effect is the best if there is moderate rainfall after soil treatment, but the chemicals with high rainfall or strong leaching can reduce the control effect due to rainfall, and may increase the drug damage, and even pollute the groundwater.

③ because things have two sides.

Therefore, in practice, according to the varieties and characteristics of pesticides, the basic characteristics of disease and Cordyceps and various factors in the environment, we must comprehensively consider, make full use of all favorable factors, control or avoid unfavorable factors, and use pesticides timely and reasonably in order to obtain satisfactory control effect.

4. Factors related to dispensing and spraying operation

Spray method

The atomization degree of the solution is mainly achieved by instruments, and the size of the droplets is directly related to the performance of the medicine. at the same time, the spraying method also directly affects the deposition of pesticides on the target.

In the process of spraying, the concentration of the spray must be consistent.

Dispensing water

The hardness of ① water refers to the amount of calcium and magnesium salts dissolved in the water. The effect of hard water on the performance of liquid medicine mainly includes the following aspects:

A: it affects the stability of emulsion and suspension; the powder particles of wettable powder will polymerize and produce larger powder pellets.

B: some agents can be converted into insoluble substances in hard water and lose their efficacy.

The electrolytes in ② water also affect the emulsification, such as the content of sodium chloride.

The acidity and alkalinity of ③ water will also have an effect on the medicament, the greater the hardness of the water, the greater the alkalinity, and some agents can be decomposed in alkalinity. For example, organophosphorus\ carbamates\ pyrethroids are sensitive to alkaline water.

Therefore, the natural water source with low hardness should be selected for spray, and the Nonionic surfactant with strong resistance to hard water should be used as emulsifier.

(source: salesman's compilation of plant protection knowledge)

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