Abstract:【Objective】Green peach aphid and peach mealy aphid are pests that cause significant harm to peach trees and other crops worldwide. The primarily feed by sucking plant sap, resulting in leaf damage that affects the growth, development, and photosynthesis of peach trees. Simultaneously, they pose a threat to the health and yield of peach trees and other crops by transmitting viruses. Control of peach aphids has traditionally relied on chemical methods. However, due to characteristics such as large population sizes, short life cycles, high reproduction rates, and strong migratory capabilities, these aphids have developed varying degrees of resistance to many commonly used insecticides. Therefore, monitoring the sensitivity of peach aphids to common insecticides is particularly important. This not only helps in assessing the actual effectiveness of the pesticides but also enables timely adjustments in control strategies based on the degree of resistance development. By doing so, the emergence of resistance can be delayed or avoided, leading to more precise pest management measures and thus achieving sustainability in agriculture. In order to evaluate the sensitivity of peach population to two commonly used insecticides, the populations of M. persica and H. amygdali were collected from peach orchards in different peach-producing areas in China during 2022 and 2023 to monitor the sensitivity to imidacloprid and afidopyropen.【Methods】The toxicity levels of these aphids to the insecticides were determined using the glass tube film methods. The active pharmaceutical ingredient of imidacloprid and afidopyropen were diluted with acetone to prepare a master stock solution for subsequent experimentation. An aliquot of 250 μL insecticide-acetone solution was applied to each tube (length: 7.5 cm; diameter: 1.2 cm, internal surface area: 27.51 cm2), and they were immediately rotated using a micro-rotator (American Wheaton Company) until solutions were dried. These peach aphids were treated for each concentration with three replicates, while controls were treated with acetone only. The tubes were then placed under laboratory conditions. After 24 h, mortality was recorded, and individuals were deemed dead if they showed no response when prompted with a brush.【Results】The monitoring results of 2022 showed that the M. persica population in Jiaxing city of Zhejiang province was found to be the most sensitive to imidacloprid, with an LC50 of 0.222 mg·L-1. In contrast, M. persica population from Qinhuangdao city in Hebei province, Xi’an city in Shanxi Province, and Lanzhou city in Gansu province exhibited lower sensitivity. These results suggest a significant variation in the response to imidacloprid across different geographic locations, potentially influenced by environmental and genetic factors. In a subsequent year, the M. persica population from Hangzhou city in Zhejiang province displayed the highest sensitivity to imidacloprid, though with an increased LC50 of 1.574 mg·L-1. Comparative analysis of the two year’s monitoring data revealed that the sensitivity of M. persica to imidacloprid remained relatively stable from Qingdao city in Shandong province. While a decreasing trend in sensitivity was observed in M. persica from Xianyang city in Shanxi province, underscoring the dynamic nature of pesticide resistance. As for afidopyropen, the M. persica population from Qinhuangdao city in Hebei province, was most sensitive in 2022, with an LC50 of 0.011 mg·L-1. In 2023, the M. persica from Hangzhou city in Zhejiang province was most sensitive with an LC50 of 0.159 mg·L-1. Comparative analysis found that the sensitivity of the M. persica population to afidopyropen showed an increasing trend from Lanzhou city in Gansu Province. Monitoring results of H. amygdali indicated that the population from Kunming city in Yunnan province exhibited the highest sensitivity to both imidacloprid and afidopyropen. This observation is crucial as it points to possible interspecies differences in how resistance mechanism are developed and managed. In contrast, the sensitivity of H. amygdali to imidaclorpid significantly decreased from Qinhuangdao city in Hebei province and Suzhou city in Anhui province, highlighting the need for ongoing monitoring and adaptive management strategies.【Conclusion】The results of this study indicate significant regional and annual variations in the susceptibility of M. persica and H. amygdali to common used insecticides imidacloprid and afidopyropen, respectively. These variations may be associated with factors such as the history of insecticides usage, environmental conditions, and the genetic diversity within populations. Therefore, it is imperative to consider these factors when devising pest control strategies, implementing targeted measures to enhance control efficiency and slow down the development of resistance. This comprehensive approach will not only clarity the causes behind the varying pesticides sensitivities but also aid in the development of more effective pest management strategies. Moreover, continuous monitoring of the changes in pest sensitivity to insecticides is crucial for effective pest management and sustaining agricultural development. Rotating insecticides with different mechanisms of action, reducing the frequency of specific insecticide usage, and conducting in-depth research into the molecular mechanisms behind reduced sensitivity in specific regions will contribute to delaying the development of insecticide resistance in pests.
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