Development of neonicotinoid resistance in the cotton aphid Aphis gossypii (Hemiptera: Aphididae) in Japan

A neonicotinoid-resistant Aphis gossypii Glover population was first detected from cucumber and sweet pepper crops in Miyazaki Prefecture, Japan, in April 2012. In this study, we determined the insecticide susceptibility of five field-collected populations of A. gossypii to seven neonicotinoids. Insecticide susceptibility was determined by performing bioassays and using the seedling-treatment method. Insecticide susceptibility of a susceptible population of A. gossypii, originally collected from a cucumber field in 2008, was also determined. High mortality (96.4–100 %) was observed in the susceptible population for the seven insecticides. In contrast, the mortality rate of the five field-collected populations collected in 2012 was low for five of the seven neonicotinoid insecticides tested: imidacloprid (26.7–65.5 %), dinotefuran (0–27.3 %), clothianidin (20.0–35.7 %), thiamethoxam (7.1–42.3 %), and nitenpyram (6.7–32.1 %). Mortality was 86.2–100 % for acetamiprid and 90.2–100 % for thiacloprid. The resistance ratio in comparison with the susceptible population was the highest for clothianidin (687-fold), lowest for thiacloprid (17-fold), and ranged from 43- to 253-fold for the other five neonicotinoids. Thus, the frequency of insecticide use needs to be reduced and other insecticides need to be employed in order to prevent the development of resistance to these two insecticides in the future.