Insecticide resistance monitoring of Aphis spiraecola (Hemiptera: Aphididae) to neonicotinoids and abamectin in a major apple-growing region.

Aphis spiraecola is a significant pest of fruit trees worldwide, causing substantial yield and economic losses in apple production. The control of A. spiraecola primarily depends on chemical pesticides; however, long-term field monitoring of insecticide resistance is lacking. This study assessed the susceptibility of a laboratory-susceptible strain (SS) of A. spiraecola to abamectin, imidacloprid, thiamethoxam, and acetamiprid. The LC50 values of A. spiraecola to abamectin, imidacloprid, thiamethoxam, and acetamiprid were 0.13, 1.44, 1.76, and 1.19 mg L-1, respectively. The resistance levels of 8 A. spiraecola field populations in a major apple-growing region were investigated in 2021 to 2023. The resistance ratios (RR) varied in different years and regions. The resistance level of A. spiraecola in the XP (Xingping) region to abamectin was the highest (RR = 42.08) in 2021. Most field populations displayed low or moderate levels of resistance to 3 neonicotinoids. However, the field population of A. spiraecola in LQ (Liquan) region had a high resistance level to thiamethoxam in 2021 with an LC50 of 109.63 mg L-1 and a resistance ratio of 62.29. The resistance levels of A. spiraecola to 4 pesticides were found to be decreasing in 3 yr. Compared to the SS strain, the field populations of A. spiraecola showed no mutations in nAChR, GABA receptor, or GluCl, suggesting that target site insensitivity may not contribute to the resistance. This study can contribute to the rational use of chemical insecticides for controlling A. spiraecola, thereby reducing economic losses in apple production and minimizing environmental pollution.