Control efficacy of eight insecticides on Myzus persicae (Hemiptera: Aphididae) and insecticide resistance development of aphid populations collected from kimchi cabbage in South Korea

Insecticide control efficacy was investigated with Myzus persicae (Hemiptera: Aphididae) populations collected on kimchi cabbage across South Korea, and their insecticide resistance levels were evaluated. Using a standard leaf-dip bioassay, the lethality at recommended active ingredient rate and lethal concentration 50 (LC₅₀) were acquired. Then, the resistance ratio was calculated as ratio between LC₅₀ of field population and LC₅₀ of laboratory population. Finally, regression analysis was conducted between the log-scaled resistance ratio and the lethality to address associations between the two estimators. Overall, sulfoxaflor and spirotetramat were the most effective insecticides, where > 80 % lethality was observed from almost all local populations. Nevertheless, five out of 12 local populations showed the resistance ratio > 5 to sulfoxaflor, suggesting resistance development to the insecticide. Imidacloprid and pyrifluquinazon also offered effective means to control M. persicae. However, large variations in the lethality, as well as the resistance ratio, were observed in imidacloprid. Deltamethrin was the least effective at recommended active ingredient rate yielding 20.2 to 63.2 % lethality, despite its low resistance ratio values. Finally, regression analysis revealed that there was in general significant negative correlation between the resistance level and the insecticide control efficacy in the insecticides evaluated. Moreover, the insecticide control efficacy declined with substantially varying rates among the insecticides with flonicamid, thiacloprid, and deltamethrin showing steeper slopes. These results indicate that both the current control efficacy and its projected decline regarding the resistance development should be taken into account together to formulate effective and sustainable management programs against M. persicae.