Insecticide resistance status of woolly apple aphid, Eriosoma lanigerum in China

To evaluate the current situation and development of resistance of woolly apple aphid, Eriosoma lanigerum (Hausmann), to conventional insecticides in China, the sensitivity of the E. lanigerum populations from several apple orchards of Qapqal in Xinjiang, Jinan in Shandong province, Qian county in Shaanxi province, Changli in Hebei province and Feng county in Jiangsu province to chlorpyrifos, lambda-cyhalothrin and imidacloprid were investigated by using the leaf dipping method during 2012-2015. Meanwhile, the enzyme activity of esterase and glutathione S-transferase of the populations were determined. The Qapqal population in 2012 was the most susceptible sample and it was selected as a reference strain. Compared with Qapqal 2012, all the other populations developed different levels of resistance to imidacloprid with the highest level found in Qapqal and Feng populations in 2015 (resistance ratio, RR >2000 fold). As to lambda-cyhalothrin, the aphid populations found in Qian, Changli and Qapqal at 2014 were susceptible, while the populations from Jinan during different years, Feng and Qapaqal at 2015 developed medium to high levels of resistance. With regard to chlorpyrifos, Qian population exhibited susceptibility, while Qapaqal, Jinan, Changli and Feng populations exhibited low to high levels of resistance. The investigation of the detoxification enzyme activity indicated that there was significant correlation between resistance levels of imidacloprid and lambda-cyhalothrin and the activity of glutathione S-transferase, respectively. However, the similar correlation was not observed with esterase. The results demonstrated that most of the tested populations of E. lanigerum developed different levels of resistance to three tested insecticides, showing a tendency to increase yearly; the resistance level to imidacloprid was the highest; and reasonable rotation of insecticides should be used in the control of E. lanigerum.