Brief Analysis of Herbicides
What are herbicides?Herbicides refer to agents that can completely or selectively kill weeds, and are used to eliminate or inhibit plant growth, also known as herbicides.
Herbicides have the characteristics of high efficiency, low toxicity, broad spectrum, and low dosage. According to their characteristics, they can be divided into selective herbicides and destructive herbicides.
Herbicide Development
The beginning of chemical weeding in farmland can be traced back to the end of the 19th century. When preventing and controlling grape downy mildew in Europe, it was occasionally found that Bordeaux mixture could harm some cruciferous weeds without harming cereal crops; France, Germany, and the United States also discovered sulfuric acid and sulfuric acid The herbicidal effect of copper, etc., and used for weeding in wheat and other places. The organic chemical herbicide era began in 1932 with the discovery of the selective herbicide dinitrophenol. The emergence of 2,4-D in the 1940s greatly promoted the rapid development of the organic herbicide industry. Glyphosate, which was synthesized in 1971, has a broad herbicidal spectrum and no pollution to the environment, and is a major breakthrough in organophosphorus herbicides. Coupled with the emergence of a variety of new formulations and new application techniques, the herbicidal effect has been greatly improved. In 1980, herbicides accounted for 41% of the total sales of pesticides in the world, surpassing insecticides and ranking first.
Among them are O-isopropyl-N-phenylcarbamate [O-isopropy-N-phe-nylcarbamate, abbreviated IPC: C6H5NHCOOCH-(CH3)2], sodium dinitro-O-cresol, etc. The most famous herbicide with auxin effect is 2,4-D, which is believed to disrupt the hormone balance in plants and cause physiological disorders, but it is a very effective herbicide for plants other than Gramineae. It is generally believed that this selectivity is determined by the strength of the detoxification effect of the plant species on 2,4-D, or because the concentration of 2,4-D varies with different plant species.
Characteristics of Herbicides
1. The herbicide has super penetrating power, which can make the active ingredients of the herbicide quickly penetrate the soil layer and completely remove all kinds of weeds.
2. Mixed use of herbicides and herbicides in wheat fields can effectively remove all kinds of weeds, such as; Chickweed, vetch, oatmeal, wild oats, barley, brome, oyster, etc.
3. Herbicides and cornfield herbicides can be effectively removed after mixed use; crabgrass, foxtail, purslane, cassava, sedge weeds have a good effect
4. Mixed use of herbicide and bean field herbicide can effectively eradicate broad-leaved weeds
5. The mixed use of foliar fertilizer can greatly improve the fertilizer efficiency and prevent windshield. Herbicides with different components have different effects. Therefore, it is recommended that farmers choose herbicides according to the needs of crops.
Classification of herbicides
Classification according to mode of action
1. Selective herbicide: Herbicides have different degrees of resistance to different types of seedlings. This agent can kill weeds but is harmless to seedlings. Such as Gai Cao Neng, trifluralin, promethazine, simazine, guoer herbicide and so on.
This type of herbicide has different selectivity between weeds and crops under certain conditions and dosage, that is, to protect crops and eliminate weeds. Most organic herbicides are selective.
2. Killing herbicides: Herbicides are toxic to all plants, as long as they touch the green parts, regardless of seedlings and weeds, they will be injured or killed. It is mainly used before sowing, before emergence after sowing, and on the main and auxiliary roads of nurseries. such as glyphosate.
These herbicides are non-selective to weeds and crops, and can kill weeds and harm crops. Most inorganic herbicides are herbicides that kill.
3. Selectivity and non-selectivity are relative, not absolute, and can change under certain conditions. If the dosage is increased or the method of use is changed, the selectivity can become destructive.
Classification according to the movement of herbicides in plants
(1) Contact herbicides: When the pesticide comes into contact with weeds, it only kills the part that is in contact with the pesticide, and plays a local killing effect, and the plant cannot conduct it. It can only kill the above-ground parts of weeds, and the effect is poor on the underground parts of weeds or perennial deep-rooted weeds with underground stems. Such as fenfen, paraquat, etc.
(2) Systemic herbicides: After the herbicide is absorbed by the roots or leaves, bud sheaths or stems, it is transmitted to the plant and causes the plant to die. Such as glyphosate, promethazine and so on.
(3) Integrated systemic conduction and contact herbicides: have dual functions of systemic conduction and contact, such as chlorben, etc.
Classification according to chemical structure
Inorganic compound herbicides: composed of natural mineral raw materials, compounds that do not contain carbon, such as potassium chlorate, copper sulfate, etc.
Organic compound herbicides: mainly synthesized from organic compounds such as benzene, alcohols, fatty acids, and organic amines. Such as ethers - fruit, s-triazines - promethazine, substituted ureas - herbicide No. 1, phenoxyacetic acids - 2-methyl-4-chloride, pyridines - gaichoon, dinitrate Anilines—trifluralin, amides—Lasole, organophosphorus—glyphosate, phenols—sodium pentachlorophenate, etc.
Synthetic Organic Herbicides
This type of herbicide is currently the most diverse, the most widely used, and the most widely used herbicide. It has the best weeding effect and is developing rapidly.
microbial herbicide
This is a class of herbicides made from living microorganisms or metabolites, such as Lubao No. 1, etc.
Plant-based herbicides
This type of herbicide uses plant extracts or metabolites to prevent or inhibit the growth of other weeds, and some are called different species of biomass, such as cinnamic acid derivatives coumarin, phenolic acids, etc.
Classified by usage
(1) Stem and leaf treatment agent: mix the herbicide solution with water, and spray it evenly on the plants with fine mist droplets. The herbicide used in this spraying method is called stem and leaf treatment agent, such as gaicaonen, glyphosate, etc. .
(2) Soil treatment agent: Spray the herbicide evenly on the soil to form a certain thickness of the drug layer. When the young shoots, seedlings and roots of the weed seeds are contacted and absorbed to play a herbicidal effect, the effect of this effect is Herbicides, called soil treatment agents, such as simazine, promethazine, trifluralin, etc., can be applied by spraying, pouring, or poisonous soil.
(3) Stem leaf and soil treatment agent: it can be used for stem leaf treatment and soil treatment, such as atrazine, etc.
Classified by application time
(1) Pre-sowing treatment agent: refers to the closed treatment of the ten soils before the crops are sown, such as eating trifluralin in the cotton field and using wild dicamba in the wheat fields, all spraying the herbicide on the ten soils before the cotton or wheat sowing , and mixed into the soil to a certain depth, so that the young roots and shoots of weeds can be absorbed, and it can control and reduce the volatilization and photolysis loss of herbicides.
(2) Pre-emergence treatment agent after sowing: that is, soil treatment is carried out before the emergence of crops after sowing. This method is mainly used for weed sprouts and young leaves to absorb herbicides that are transmitted to the growth point, and is safe for crop buds.
(3) Post-emergence treatment agent: refers to spraying the herbicide directly on the weed plants after the weeds emerge. There are also some herbicides that kill weeds, such as paraquat and glyphosate, which can be used to kill weeds in the middle and late stages of growth. Post-emergence herbicides are generally herbicides that are absorbed by stems and leaves and can be transmitted to other parts of the plant.
(5) Classified by chemical structure.
According to the classification of chemical structure, it mainly refers to organic synthetic herbicides, with incomplete statistics, there are nearly 20 categories, including amides, anilines, substituted ureas, phenoxys, benzoic acids, carbamates, diphenyl ethers, three Aminobenzenes, organophosphorus, heterocyclics, etc.
Herbicide Handling Techniques
Compared with insecticides and fungicides, herbicides have higher requirements for the application technology. Improper use of insecticides and fungicides may only affect the control effect. The improper use of herbicides is related to the safety of crop growth.
Strictly control the sensitivity of crops to herbicides. Different crops have different sensitivities to herbicides. If the pesticides are not selected according to the sensitivity of the crops to herbicides, even if the herbicides that are safe for the crops are used, phytotoxicity may easily occur sometimes. Generally, herbicides for controlling broad-leaved weeds are sensitive to dicotyledonous crops, and herbicides for controlling gramineous weeds are sensitive to gramineous crops. For example, 2,4-D, dimethyltetrachloride, etc. have good effects on broad-leaved weeds, but are sensitive to broad-leaved crops such as cotton, rape, melons, beans, peanuts, potatoes, tobacco, etc., and are prone to phytotoxicity . Acetochlor is suitable for broad-leaved crops such as corn, peanuts, cotton, and soybeans, but it is prone to phytotoxicity to wheat. Gaicaoneng, Wenshade, Hecaoke, etc. are effective in controlling grass weeds in broad-leaved crop fields, but they are seriously harmful to grass crops such as wheat, rice, millet, and corn.
Strictly control crop sensitive period and application period. Crops have different sensitivities to insecticides and fungicides, and even more to herbicides, at different growth and development stages. Under normal circumstances, crops are particularly sensitive to herbicides during germination, before 3 leaves, and flowering and filling stages, and phytotoxicity is prone to occur in these periods. Pre-emergence herbicides can only be absorbed through the radicle, coleoptile or hypocotyl of weeds, and kill weeds. When used after weeds emerge, they generally have no or very low herbicidal effect. Post-emergent herbicides must also be used at a certain growth stage of the weed or crop to be safe and effective. For example, Gaicao can be used at the 3-5 leaf stage of weeds, and the control effect on gramineous weeds is usually 90-100%, but the effect is lower when used after the 5-leaf stage.
Strictly choose the type of herbicide. There are several types of herbicides, which should be selected according to grass conditions.
⑴ Selective herbicides: These herbicides can be used within a certain dosage range to selectively kill some harmful plants, and the crops are safe. Proper use in crop fields can achieve the purpose of only killing weeds without harming crops.
⑵ Killing herbicides: This kind of herbicides can kill all plants, such as Kewuzong, sodium pentachlorophenate, glyphosate, etc. This type of herbicide is limited to weed control in fallow fields and vacant land.
⑶Contact herbicides: This type of herbicide only harms the part of the plant that has been exposed to the chemical, and has no effect on the part that has not been exposed to the chemical, such as Kewuzong, Propanil, and Biben.
⑷ Systemic conduction type herbicide type: the active ingredients of this type of herbicide can be absorbed by the roots, stems and leaves of plants, and quickly spread to the whole plant, thereby killing harmful plants, such as glyphosate, glyphosate, stable killing Ether etc.
Strictly control the dosage and concentration of herbicides. The selectivity of herbicides is the selectivity within a certain dosage range, so even if it is a selective herbicide, it will cause phytotoxicity to crops beyond the specified dosage range. For example, the dosage of 60% butachlor EC in rice seedling fields exceeds 0.15 liters/mu, the dosage of 48% trifluralin in cotton seedbeds exceeds 0.1 liters/mu, and the dosage of 10% oxachlor in rice seedling fields exceeds 0.3 liters/mu. Within 10 days after planting, the dosage of 50% weluosheng exceeds 0.3 liters/mu, etc., which will cause phytotoxicity of crops. 2,4-D butyl ester has a certain selectivity to wheat, but when the amount is too large, it will also kill the wheat or make the wheat plant seriously deformed, affecting the yield. In addition, whether the dosage of herbicides is appropriate is also affected by factors such as crop species, soil texture, climatic conditions and application methods. If the herbicide is used at a high concentration, it must not be re-sprayed, otherwise it will easily cause the local application concentration to be too high, and local phytotoxicity will occur.
Strict use of herbicides. The application methods of herbicides include stem and leaf treatment, soil treatment and herbicidal film weeding. At present, the most commonly used methods are stem and leaf treatment during the growth period and pre-emergence soil treatment after sowing. Stem and leaf treatment during the growth period is a method of spraying herbicides on the stems and leaves of weeds at a certain growth stage after the emergence of crops. In this method, the herbicide not only contacts the weeds, but may also contact the crops, so the herbicide is required to have a high selectivity or directional spraying to achieve the purpose of safe application. Post-sowing and pre-emergence soil treatment is a method of spraying herbicides on the soil surface after planting and before emergence. Most soil treatments are used in this way. Stem and foliage treatment herbicides are usually inactivated quickly after falling into the soil or decomposed by microorganisms to lose herbicidal activity, while soil treatment herbicides are generally ineffective against weeds after emergence. Therefore, only by selecting the method of use according to the characteristics of the herbicide can its effect be fully exerted and negative effects avoided.
Strictly follow the principle of mixing herbicides. In production, sometimes when killing multiple weeds, several herbicides need to be mixed, but not all herbicides can be mixed. The following principles must be strictly followed in the mixed use of herbicides: The herbicide spectrum is different. ②The herbicides used in combination must have the same application period and method. ③ After the herbicide is mixed, precipitation and stratification cannot occur. ④ After the herbicide is mixed, the dosage is 1/3~1/2 of the single dosage. In addition, for herbicides that cannot be mixed with each other, the method of using them in stages can also achieve the purpose of killing weeds. Its combined application method: use herbicides alternately on the same piece of soil. For example, trifluralin is used to kill grasses first, and then culsha net is used to kill broad-leaved weeds; soil treatment is coordinated with post-emergence stem and leaf treatment.
Symptoms of herbicide damage
The symptoms of phytotoxicity caused by herbicides are variable and diverse, similar to the symptoms of certain diseases, which often lead to misunderstandings in diagnosis. Generally, phytotoxicity manifests faster than disease symptoms, and no pathogen appears. In production, the identification of herbicide damage should be strengthened.
(1) Phenoxycarboxylic acids: commonly used agents include 2,4-D, dimethyltetrachloride, 2,4-D-butyl ester, etc.
Symptoms are deformed leaves, flowers, and spikes. Leaves are thick, dark green, curly, chicken feet or onion tubular; stems are brittle and easily broken, with swollen stem bases; roots are short and thick, without root hairs, and the plants are short; in severe cases, they stop growing, the cortex cracks, flowers and fruits fall, and finally die .
(2) Aryloxyphenoxypropionic acids: Commonly used agents include Wenshade, Hecaoke, Gaiconeng, Weiba, Puma, etc.
Symptoms are mainly deformed plants, yellowish-brown growing points, purple or yellow heart leaves.
(3) Diphenyl ethers: Commonly used agents include aquatyl ether, weed funnel, and Huwei, etc.
Symptoms are brown necrotic spots on the leaves, deformed leaves in severe cases, scorched, and no new leaves.
(4) Amides: commonly used agents include Lasso, Dole, propanil, butachlor, etc.
Symptoms are yellow leaves when mild, spots on leaves when severe, curled and shrunken, and finally withered.
(5) Carbamates: Commonly used agents include carbadan, methacryl, and adenamba, etc.
Symptoms are curled leaves, many tillers, thick and short stem bases and new roots, and short plants.
(6) Substituted ureas and trichlorobenzenes: mainly chlortoluron, promethazine, simazine, etc.
Mainly chlorosis, the heart leaves and leaf tips start to turn yellow like fire, the plants are short, and the growth is slow.
(VII) Heterocycles: mainly paraquat, glyphosate, tococarb, oxaquat, bentazone, etc.
Symptoms are leaf discoloration, yellowing, and finally plant death.
Causes of herbicide damage
1. Improper selection of herbicide types All kinds of herbicides have corresponding herbicidal spectrum and applicable environment. Failure to select herbicides according to the weed types and the specific conditions of the farmland will make the selected herbicide species powerless or unable to exert its weeding ability.
2. The quality of herbicides is unqualified All kinds of herbicides have corresponding quality standards, the most important of which are the content of active ingredients, types of impurities and their content, dispersibility, emulsification, stability, etc., which directly affect the efficacy and injury of the herbicides. . Producers and operators are responsible for pesticide efficacy and injury caused by pesticide quality problems.
3. The problem of application dosage There are several reasons for the incorrect dosage. First, the subjective behavior of farmers always suspects that the dosage is low. The weeding effect is not good, and the dosage is increased to above the limit. Inevitably, the second is that in order to explain the low cost of its products to adapt to the objective fact that farmers have low purchasing power, the dosage recommended in the instructions is very low, which cannot guarantee the weeding effect. The area does not match. The fourth is uneven spraying, heavy spraying, and missing spraying. Especially when using a multi-nozzle sprayer, the amount of liquid sprayed by each nozzle is different, which directly leads to uneven spraying.
4. Improper application period The sooner the stem and leaf treatment agent is applied after weed emergence, the better the effect. The later the soil treatment agent is applied before weed emergence, the better the effect, but the possibility of phytotoxicity to crops is also greater.
5. Wrong application method Most of the soil treatment agents will cause phytotoxicity when used for stem and leaf treatment, and a few will be ineffective. Most of the stem and leaf treatment agents will be ineffective when used for soil treatment. The possibility of phytotoxicity is very small.
6. Unsuitable environmental conditions
①Sandy soil with soil organic matter content less than 2% is prone to phytotoxicity in closed treatment. The organic matter content is higher than 5%, and the efficacy is very low.
②The possibility of heavy rain and phytotoxicity after the sealing treatment agent is applied is high, and the stem and leaf treatment should be re-sprayed.
③ The possibility of phytotoxicity increases as the herbicidal effect decreases with continuous low temperature.
④The efficacy of the soil drought sealing treatment agent is reduced or even invalid.
⑤ In the windy days above level 3, pesticide application cannot ensure uniform spraying, and the efficacy of pesticides may decrease, and phytotoxicity may occur.
⑥The quality of land preparation is not good, and the effect of closed treatment is not good.
Herbicide damage prevention
In order to prevent phytotoxicity caused by improper use of herbicides, it is necessary to strictly follow the use technology and standard operation.
(1) Pay attention to herbicides and sensitive crops. Different crops are not uniformly sensitive to different herbicides. Herbicides for controlling broadleaf weeds are sensitive to grass crops, and broadleaf crops are sensitive to herbicides for controlling grassy weeds. For example, 2, 4-D and dimethyltetrachloride are sensitive to cotton, melons, beans, fruit trees, etc.; Gaicaoneng and Wenshade are sensitive to wheat, rice, and corn. Therefore, when using it, one must be optimistic about the instructions, recognize the characteristics and performance of the herbicide, pay attention to sensitive crops, and beware of misuse or drift of the herbicide.
(2) Pay attention to the sensitive period of crops. Under normal circumstances, crops are particularly sensitive to herbicides during germination, pre-three-leaf and flower filling stages, and are prone to phytotoxicity.
(3) Strictly control the dosage and concentration of herbicides. In order to prevent local phytotoxicity caused by excessive dosage and concentration of herbicides, when using herbicides, the liquid medicine should be sprayed evenly, the walking speed, the width and speed of the manual control spraying width should also be uniform, and the working time should not be too long.
(4) Master the key points of herbicide use technology and operation:
1. "One level": the ground should be level. The pesticide application field should be carefully cultivated to ensure that the ground is flat, without large clods, and without potholes.
2. "Two evenness": The medicine should be mixed evenly on the carrier, and the spray or poison soil should be evenly distributed.
3. "Three standards": accurate application time, accurate application amount, and accurate application plot area. For example, 40% oatmeal is used to control wild oats, and 3 kg/ha is used before sowing.
4. "Four Looks": look at seedling condition, grass condition, weather and soil quality. It is not easy to apply pesticides to unrooted or thin seedlings: use according to the type and growth of weeds; when the temperature is low, the application amount is at the upper limit of the application; the application amount is higher in sticky soil, and less in sandy soil; the soil is dry No medicine.
5. "Five Don'ts": do not apply pesticides when the seedlings are weak; do not apply pesticides when the water in the paddy field is less than 3 cm deep or submerge the heart and leaves; do not apply pesticides when the field is too dry; do not apply pesticides when there is heavy rain or when there is dew on the leaves; The paddy field leaks water and does not apply pesticides.
(5) Master the properties of pharmaceuticals. Grasp whether the agent is volatile, photolyzed, and whether it is prone to physical or chemical reactions in the soil.
(6) Clarify the "main attack position". The "main attack parts" of herbicides for general soil treatment are the weeds just germinated, young stems and leaves, that is, before the third leaf. However, sultrapyr is treated with stems and leaves during the weeds' peak period, absorbed by stems and leaves and then transmitted to other tissues.
(7) The medication time is reasonable. For example, propanil is at the 2-leaf stage, butachlor is 2-3 days before sowing, and the effect of Kewuzong and glyphosate increases with the increase of weed leaf area.
(8) Play the role of water. Xicaojing, Guoer, Hedazhuang, Nongdeshi, etc. keep the water layer 4-6 cm after application, which can exert the efficacy without causing phytotoxicity; produce harm.
(9) Disorderly use is prohibited. The mixed use of herbicides can improve the efficacy and expand the herbicidal spectrum, but blind mixed use can easily cause phytotoxicity. For example, propanil cannot be mixed with organophosphorus or carbamates; dimethyltetrachloride cannot be mixed with acidic pesticides, etc.
(10) Cleaning spray equipment. Sprayers that have been sprayed with herbicides should be cleaned. They can be rinsed with clean water first, then washed several times with soapy water or 2-3% alkaline water, and finally rinsed with clean water.
Herbicide Mixing Conditions
The mixed use of herbicides and their mutual chemical reactions will affect the effect of herbicides. Know how they interact to get the best out of your mix.
When different herbicide varieties are used in combination, the herbicides will interact, and the interaction types can be divided into: additive effect, synergistic effect and antagonism effect.
1. Additive effect: Additive effect means that the actual herbicidal effect of the two herbicides mixed is equal to the sum of the herbicidal effects of the two herbicides alone calculated according to the relevant model.
2. Synergistic effect: synergistic effect means that the actual herbicidal effect of the mixed application of two herbicides is greater than the sum of the herbicidal effects of the two herbicides used alone calculated according to the relevant model.
3. Antagonism: Antagonism means that the actual herbicidal effect of the mixed application of two herbicides is less than the sum of the herbicidal effects of the two herbicides used alone calculated according to the relevant model.
interactive judgment method
According to the definition of different interaction types above, the judgment of the interaction type between herbicides is affected by the calculation method (correlation model) of the theoretical value of the joint action between herbicides. The theoretical values calculated by different models are different, which may lead to different interaction types. Two commonly used models are the dose-plus model and the survival-product model.
1. dose-addition model
The dose-addition model assumes that one herbicide is replaced by another herbicide at an equivalent dose, with no change in toxicity. Figure 5-6-1 is the isobologram, which more intuitively represents the dose-addition model. The effective median dose (ED50) of herbicide A and herbicide B The straight line connecting the two points is the equibolism of the effective median dose of the combined action of these two herbicides. If the observed value of the mixture of two herbicides is on this equivalent line, then the interaction between the two herbicides is additive; The interaction between the two herbicides is synergistic; the interaction between the two herbicides is antagonistic if the observed value of the combination of the two herbicides is above this isobolism.
2. survival product model
The equivalence model predicts the interaction as a linear equivalence line. Gowing (1959) questioned the additive model and believed that the interaction isobolism is not a straight line. He proposed the following formula to calculate the mixed effect of herbicides:
E = X + Y(100-X)/100
Where E is the theoretical growth inhibition percentage of herbicide A and herbicide B mixed, X is the growth inhibition percentage of herbicide A alone, Y is the growth inhibition percentage of herbicide B alone.
If calculated directly with the relative weight of the treated plants (percentage of the control), the above formula can become:
E1 = X1Y1/100
Wherein, E1 is the theoretical relative weight of herbicide A and herbicide B mixed, X1 is the relative weight of herbicide A alone, and Y1 is the relative weight of herbicide B alone. This calculation method was proposed by Colby in 1968, so it is called the Colby method. This method is widely used.
Generally speaking, if the two herbicides have the same mechanism of action, it is more reasonable to use the additive model to calculate. If the mechanism of action of the two herbicides is different, it is more reasonable to use the survival product model to calculate.
Precautions when mixing herbicides
1. On the basis of fully understanding the characteristics of herbicides, according to the purpose of weeding, select the appropriate herbicides for mixed use.
2. In general, there should be no antagonism between the mixed herbicides. In individual cases, antagonism can be used to improve the safety of crops, but the herbicidal effect should be guaranteed.
3. The mixed herbicides should be physically and chemically compatible, neither physical phenomena such as stratification, crystallization, aggregation, and segregation should occur, and the active ingredients should not undergo chemical reactions.
4. Using synergistic effects between herbicides to increase activity against weeds also increases activity against crops. Therefore, care should be taken to prevent phytotoxicity of crops.
Herbicide Application Interval
For plots intended to plant eggplant, pepper, cabbage, radish, cabbage, and cabbage, if the previous stubble has been used, imazethapyr must be planted at an interval of 40 months; chlorsulfuron must be planted at an interval of 36 months; For Nicosulfuron, the active ingredient per hectare exceeds 60 grams, that is, 4% nicosulfuron exceeds 100 milliliters per mu, and must be planted at an interval of 18 months; when sulfaflufenacil is used, the active ingredient is 48-60 grams per hectare, that is For 80% fomesafen 3.2-4 grams per mu, planting should be done at intervals of 26 months; if fomesafen is used, the dosage of active ingredient is 375 grams per hectare, that is, 25% fomesafen is 100 ml per mu, and planting should be done at intervals 18 months of planting; used metsulfuron-methyl, the active ingredient per hectare exceeds 7.5 grams, and must be planted at an interval of 24 months; has used isoxaflutole, and the active ingredient exceeds 71 grams per hectare, and must be planted at an interval of 18 months .
In addition, quinclorac has been used in the previous crop, and the active ingredient per hectare is 106-177 grams, and peppers, eggplants, and radishes must be planted at intervals of 24 months. , that is, 70% metrizone is 33-67 grams per mu, and radishes must be planted at intervals of 18 months.
Potatoes For the plots where potatoes are intended to be planted, if imazethapyr has been used in the previous stubble, the planting interval must be 36 months; if chlorimuron-methyl has been used, the interval must be planted 40 months; if nicosulfuron has been used, the interval must be planted 12 months; For fomesafen, the active ingredient is 375 grams per hectare, that is, 25% fomesafen is 100 ml per mu, and must be planted at intervals of 24 months; metsulfuron-methyl has been used, and the active ingredient per hectare exceeds 7.5 grams, and intervals are required 34 months of planting; used simazine, the active ingredient per hectare exceeds 2.24 kg, that is, 50% simazine exceeds 300 grams per mu, and must be planted at intervals of 24 months; used atrazine, active ingredient per hectare More than two kilograms, that is, more than 350 ml of 38% atrazine per mu, must be planted at intervals of 24 months; used chlorsulfuron, the active ingredient is 15 grams per hectare, and must be planted at intervals of 24 months; used quinclorac , the amount of active ingredients per hectare is 106-177 grams, and the planting interval must be 24 months.
Herbicide Influencing Factors
With the modernization of agriculture, farmers also use a large number of high-tech products in agricultural production, such as a series of chemical products such as biological pesticides and pesticide mixtures, but the most popular pesticide products are herbicides, so the sales of herbicides have always been Ranked first among pesticides. However, there are many varieties of herbicides on the market, and at the same time, the application technology is also demanding. If there is a little carelessness in the application, problems such as phytotoxicity and poor weeding effect will occur. Then, how to master the selection of herbicide varieties and its application technology is the key to improving the weeding effect of herbicides.
How to improve herbicide weed control effect:
1. Choose a suitable herbicide Because each herbicide has a certain herbicidal spectrum, it is destructive and selective. Therefore, effective herbicides should be selected according to the types of crops and the main species of weeds. At the same time, the herbicide should be selected according to the farming system. In addition, pay attention to mixing and alternating herbicides. Since the continuous use of the same herbicide for many years will easily lead to the gradual reduction of sensitive weeds and the increase of drug-resistant weeds. Therefore, herbicides must be used in combination and alternately between years to achieve the goal of long-term weed control.
2. Select the best time to apply pesticides. According to the nature of herbicides, the weed occurrence period, the growth period of weeds and crops, select the appropriate period of application. There are many kinds of herbicides, including stem and leaf treatment agents, soil treatment agents, contact herbicides, and herbicides that kill herbicides. Some are suitable for preemergent weeding, and some are suitable for stem and leaf weeding. Soil treatment involves spraying herbicides directly on the soil surface to kill newly germinated weeds. For example, Dole, acetochlor, etc. should be applied before the weeds emerge after the crops are sown, and wait until the weeds emerge. Not only the effect is poor, but some will damage the crops. Therefore, it is very important to select the best time for herbicide application.
3. The effect of herbicide use is directly proportional to the temperature. When the temperature is high, the weeds have a strong ability to absorb and transport herbicides, and the herbicide activity is also high, and it is easy to fully exert the herbicide effect on the action site of the weeds. The test results show that when the herbicide is applied, the higher the air and soil temperature, the more significant its efficacy, especially the herbicidal effect of the stem and leaf treatment herbicide can be greatly improved, and the use of herbicides in low temperature weather conditions Not only will the effect be significantly reduced, but the detoxification effect in crops will be slow due to the low temperature, which will easily induce phytotoxicity. The appropriate temperature for applying herbicides is 20-35°C, and the air humidity will also affect the efficacy of herbicides. The effect is obvious. Applying stem and leaf herbicides when the air humidity is relatively high can prolong the residence time of the herbicide on the weed leaf surface, help the weed leaf surface stomata to open, thereby absorbing a large amount of herbicide, and improving For the purpose of herbicidal effect, after the soil treatment herbicide is absorbed, it will be transported upward with a large amount of water, which is beneficial to inhibit photosynthesis, and can significantly improve the herbicidal effect. Therefore, when using herbicides, the greater the humidity of the air, the more obvious the weeding effect; otherwise, the weeding effect will be reduced.
The price of herbicides
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