Since its inception, chemical pesticides have played a huge role in the control of plant diseases and insect pests. However, due to the long-term repeated use and abuse of pesticides, many pesticides have been used in the prevention and control of plant diseases and insect pests, and the effects of drug efficacy have decreased or even become ineffective. The emergence of drug resistance will not only have a serious negative impact on the efficacy of pesticides, but also increase production costs, reduce the effectiveness of prevention and control, and also affect the ecological balance of nature due to blind drug use. Therefore, in order to reduce the occurrence of plant resistance, the following investigations must be conducted, and test comparison methods and methods must be adopted to accurately determine whether drug resistance has occurred.
1. Whether the efficacy of the drug continues to decrease.
The emergence of drug resistance is generally not sudden without warning. Before the phenomenon of severe decline in efficacy, there must be a process of continuous decline in efficacy, which is long and short due to different pests and diseases. For example, the resistance to carbendazim is quite rapid, but it takes two or three years for the drug to continue to decrease and eventually become ineffective. Resistance to carbamate insecticides, such as the rice planthopper, is much slower and takes a considerable amount of time.
The development of drug resistance is generally not leaping, but continuous. For example, the second medication is resistant, the third medication does not develop resistance, and the fourth medication occurs again. This kind of leaping and sporadic "drug resistance phenomenon" is a matter of course, and it should be ruled out that some of the non-resistance phenomenon of drug efficacy is mistaken for the problem of drug resistance.
The occurrence of drug resistance should be basically the same in the same biological population. If in the same plot, one part of the field is effective and the other part of the field is very poor, in this case, the judgment of "drug resistance" cannot be made lightly. As long as the crop variety and farming conditions are basically the same, the performance of resistance is generally not very different.
2. Whether to use certain drugs for a long time.
A medicament is continuously used on a pest for at least one year and is used repeatedly several times a year. For a large number of generations of pests occurring within a year, such as aphids, mites, whiteflies, mosquitoes, and flies, up to dozens of generations a year, if the same agent is frequently used for the same pest, resistance appears. The probability is higher. However, this is related to the type of medicine. Some of the drug resistance development is rapid, and some development is slower. For pests with few generations in a year, such as a variety of lepidopteran and coleopteran pests, it is often necessary to continue to use it for several years before it can show resistance.
3. Whether the speed of the increase in the number of insects is increasing.
After each use of the drug, the rate of increase in the number of insects is significantly faster than in the past, and consideration should be given to whether or not drug resistance has occurred. Before the emergence of drug resistance, the agent has a strong killing power against pests, and the mortality rate after pest poisoning is high, so the insect density will be quickly pressed down. After a long period of time, a small number of remaining pests can reproduce. , to achieve a considerable density of insects. However, after the occurrence of drug resistance, the increase in the density of the insect population will be significantly accelerated due to the increase in the number of remaining pests. In addition, some of the pests have resilience because they have the ability to resist drugs, although they are poisoned but not dead.
4. Whether the effective use of the drug is gradually increasing.
If the same pesticide is used, and if the pesticide is accurately measured and the method of use is correct, if there is a significant increase in the effective use concentration of the agent or the effective use dose per acre, the drug resistance problem should be considered. Due to the emergence of drug resistance, the original effective use concentration or dose can not achieve the control effect that can be achieved originally, and thus gradually increase. However, it should be stated that if the efficacy of the pesticide is incorrectly measured or the method of use is not effective, it cannot be used as a basis for judging the drug resistance.
5, drug efficacy comparison test and virulence determination.
In the above cases, after the obvious decrease in efficacy or increase in the amount of drug, in order to confirm whether the drug is a drug-resistant phenomenon, it can also be used as a comparison test for the efficacy of the community or a virulence test.
In the field, the plots with relatively flat and uniform fertility and relatively uniform plant growth are divided into several plots (16.7 square meters per plot). Generally, 3 to 5 cells are used as a treatment zone for a concentration of 3 to 5 drugs (or a dose per unit area). Before the application, the number of insect populations in each district was investigated, and the concentration of 3 to 5 pesticides was prepared. The lowest concentration was the concentration used in the habit, and the other concentrations were increased by 20%, 40%, 60%, 80%, respectively. 100%, etc., based on the actual increase in concentration that has been noted.
The prepared liquid is accurately sprayed in the corresponding community. After 24 hours, the number of remaining insects in each plot is checked, and compared with the number of insect bases before application, the population reduction rate or control efficiency is calculated. If necessary, the survey can be conducted a second time after 48 hours.
According to the test results, the change of the control effect of each treatment cell can be sorted out. If the concentration of the customary concentration (ie the lowest concentration used in the test) is indeed reduced, and the results of the three replicates are similar, and the control effects in the various treatment zones with increased concentrations are correspondingly improved, then the preliminary judgment can be made. There is indeed a problem with drug resistance. In this way, the immersion virulence measurement can be performed for further diagnosis.
China Cooperation Times
1. Whether the efficacy of the drug continues to decrease.
The emergence of drug resistance is generally not sudden without warning. Before the phenomenon of severe decline in efficacy, there must be a process of continuous decline in efficacy, which is long and short due to different pests and diseases. For example, the resistance to carbendazim is quite rapid, but it takes two or three years for the drug to continue to decrease and eventually become ineffective. Resistance to carbamate insecticides, such as the rice planthopper, is much slower and takes a considerable amount of time.
The development of drug resistance is generally not leaping, but continuous. For example, the second medication is resistant, the third medication does not develop resistance, and the fourth medication occurs again. This kind of leaping and sporadic "drug resistance phenomenon" is a matter of course, and it should be ruled out that some of the non-resistance phenomenon of drug efficacy is mistaken for the problem of drug resistance.
The occurrence of drug resistance should be basically the same in the same biological population. If in the same plot, one part of the field is effective and the other part of the field is very poor, in this case, the judgment of "drug resistance" cannot be made lightly. As long as the crop variety and farming conditions are basically the same, the performance of resistance is generally not very different.
2. Whether to use certain drugs for a long time.
A medicament is continuously used on a pest for at least one year and is used repeatedly several times a year. For a large number of generations of pests occurring within a year, such as aphids, mites, whiteflies, mosquitoes, and flies, up to dozens of generations a year, if the same agent is frequently used for the same pest, resistance appears. The probability is higher. However, this is related to the type of medicine. Some of the drug resistance development is rapid, and some development is slower. For pests with few generations in a year, such as a variety of lepidopteran and coleopteran pests, it is often necessary to continue to use it for several years before it can show resistance.
3. Whether the speed of the increase in the number of insects is increasing.
After each use of the drug, the rate of increase in the number of insects is significantly faster than in the past, and consideration should be given to whether or not drug resistance has occurred. Before the emergence of drug resistance, the agent has a strong killing power against pests, and the mortality rate after pest poisoning is high, so the insect density will be quickly pressed down. After a long period of time, a small number of remaining pests can reproduce. , to achieve a considerable density of insects. However, after the occurrence of drug resistance, the increase in the density of the insect population will be significantly accelerated due to the increase in the number of remaining pests. In addition, some of the pests have resilience because they have the ability to resist drugs, although they are poisoned but not dead.
4. Whether the effective use of the drug is gradually increasing.
If the same pesticide is used, and if the pesticide is accurately measured and the method of use is correct, if there is a significant increase in the effective use concentration of the agent or the effective use dose per acre, the drug resistance problem should be considered. Due to the emergence of drug resistance, the original effective use concentration or dose can not achieve the control effect that can be achieved originally, and thus gradually increase. However, it should be stated that if the efficacy of the pesticide is incorrectly measured or the method of use is not effective, it cannot be used as a basis for judging the drug resistance.
5, drug efficacy comparison test and virulence determination.
In the above cases, after the obvious decrease in efficacy or increase in the amount of drug, in order to confirm whether the drug is a drug-resistant phenomenon, it can also be used as a comparison test for the efficacy of the community or a virulence test.
In the field, the plots with relatively flat and uniform fertility and relatively uniform plant growth are divided into several plots (16.7 square meters per plot). Generally, 3 to 5 cells are used as a treatment zone for a concentration of 3 to 5 drugs (or a dose per unit area). Before the application, the number of insect populations in each district was investigated, and the concentration of 3 to 5 pesticides was prepared. The lowest concentration was the concentration used in the habit, and the other concentrations were increased by 20%, 40%, 60%, 80%, respectively. 100%, etc., based on the actual increase in concentration that has been noted.
The prepared liquid is accurately sprayed in the corresponding community. After 24 hours, the number of remaining insects in each plot is checked, and compared with the number of insect bases before application, the population reduction rate or control efficiency is calculated. If necessary, the survey can be conducted a second time after 48 hours.
According to the test results, the change of the control effect of each treatment cell can be sorted out. If the concentration of the customary concentration (ie the lowest concentration used in the test) is indeed reduced, and the results of the three replicates are similar, and the control effects in the various treatment zones with increased concentrations are correspondingly improved, then the preliminary judgment can be made. There is indeed a problem with drug resistance. In this way, the immersion virulence measurement can be performed for further diagnosis.
China Cooperation Times
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