Reasons for the Rise in Pesticide Resistance Among Common Crop Pests and How to Respond
Drug resistance, also known as tolerance, refers to the reduced sensitivity of pathogens and tumor cells to chemotherapeutic drugs.So how should we respond to the rising pesticide resistance of common crop pests? Why does pesticide resistance develop?
How should we respond to the rising pesticide resistance of common crop pests?
1. The pesticide resistance of the brown planthopper and the striped stem borer in rice is cause for concern
According to survey data from monitoring points set up by researchers in major rice-producing areas to investigate the sensitivity of brown planthopper populations to imidacloprid and buprofezin, high levels of resistance have already developed. Compared with previous years, the resistance ratio of the brown planthopper to buprofezin has risen sharply, with resistance ratios all above 100-fold; surveys of its sensitivity to pymetrozine show medium to high levels of resistance. The striped stem borer shows low to medium levels of resistance to the insecticides chlorantraniliprole and flubendiamide, and medium to high levels of resistance to triazophos.
Recommended control measures: In controlling the brown planthopper, avoid continuous, single-agent applications. Between source and destination areas of migration, and between successive generations in the same area, insecticides with different mechanisms of action and no cross-resistance should be used alternately and in rotation. It is recommended that all rice-growing areas temporarily stop using imidacloprid and buprofezin to control the brown planthopper; strictly limit the number of times pymetrozine is used to control the brown planthopper, preferably to 1 time per rice season; and alternately rotate new agents such as nitenpyram, dinotefuran, and sulfoxaflor to delay the development of resistance in the brown planthopper. In the prevention and control of the striped stem borer, in areas where resistance has developed, take care to limit the number of applications of diamide insecticides, nereistoxin insecticides, abamectin, and similar agents, avoid exposing multiple consecutive generations to agents with the same mechanism of action, and curb the upward trend of resistance.
2. Resistance in the diamondback moth and the beet armyworm is rising rapidly
Researchers monitored the resistance of the diamondback moth to chlorantraniliprole, chlorfenapyr, indoxacarb, abamectin, and beta-cypermethrin in vegetable-producing areas, monitored the resistance of the beet armyworm to chlorantraniliprole and methoxyfenozide, and monitored the resistance of the tobacco whitefly to spirotetramat and cyantraniliprole. The survey results show that: in southern vegetable-producing areas, pest resistance to commonly used field pesticides is rising rapidly compared with northern vegetable-producing areas, showing a pattern of severe in the south and mild in the north; diamondback moth populations have developed high levels of resistance to abamectin and beta-cypermethrin, and medium to high levels of resistance to chlorantraniliprole, chlorfenapyr, and indoxacarb; beet armyworm populations have developed above-medium levels of resistance to chlorantraniliprole and methoxyfenozide, with resistance ratios all above 15-fold; tobacco whitefly populations have developed medium levels of resistance to the new agents cyantraniliprole and spirotetramat, with resistance ratios all above 30-fold.
Recommended control measures: First, promptly adjust the pesticide application strategy, implementing alternate rotation of agents with different mechanisms of action, with each type of pesticide used no more than 1 time per vegetable season, to delay the rate at which resistance develops. Second, strictly follow the pesticide instructions, avoiding excessive application and arbitrarily increasing the number of applications and the concentration used. Third, given that diamondback moth populations in most areas of our country have developed high levels of resistance to abamectin and beta-cypermethrin, it is recommended to suspend their use and instead rotate other agents with different mechanisms of action, such as spinetoram, diafenthiuron, and azadirachtin.
Why do common crop pests develop pesticide resistance?
1. When a single pesticide is used continuously over a long period to control a certain pest or disease, a decline in efficacy occurs. To achieve the original control effect, the application concentration must reach many times the originally required concentration. This phenomenon is called pesticide resistance in pests and diseases. At present, pesticide resistance in pests is fairly common.
2. After a pest or pathogen develops resistance to a certain pesticide, it is also resistant to another pesticide that has never been used. This phenomenon is called cross-resistance. Generally speaking, pesticides of the same type readily develop cross-resistance, while pesticides of different types, because their toxic mechanisms against pests or pathogens differ, do not readily develop cross-resistance.
3. The development of resistance is mainly caused by the continuous use of the same pesticide over many years in the same area to control that pest or disease. This is because within a pest population, individuals differ in their tolerance. After a pesticide is applied, most of the individuals with weak resistance are killed, while a few individuals with strong resistance survive and continue to reproduce. Through such repeated “selection” many times, and after a stage of adaptation and variation, a resistant population is finally formed.
4. Whether a pest has truly formed a resistant population needs to be identified by scientific methods. This is because there are many reasons for poor control effects, such as problems with pesticide quality and application technique, which can also reduce the control effect. Poor control effects cannot all be attributed to the development of resistance.
5. In the use of fungicides, there is also the problem of resistance in pathogens. Many fungicides used to control plant diseases have increasingly lower control effects. The development of resistance in pathogens is similar to that in pests, and the control measures are the same.
At present, some areas address resistant pests and pathogens by increasing the application concentration, increasing the amount used, and increasing the number of applications. This not only wastes pesticides and raises costs, but also easily causes phytotoxicity, pesticide poisoning accidents, and aggravated environmental pollution, and the resistance will also become more severe. Attention should be paid to this.