Resistance Dynamics to Three Types of Insecticides in Helicoverpa armigera Hübner in North China, and Xinjiang from 1996 to 1999

The developmental tendency of resistance to cyhalothrin, monocrotophos and methomyl in H. armigera collected from Xinjiang(Kuerle county) and North China (Jizhou county of Hebei province, Xihua county of Henan province, and Gaomi county of Shandong province) areas from 1996 to 1999 was evaluated. The results showed that cotton bollworm to three types of insecticides was susceptible or displayed low level resistance in Xinjiang population, but medium or high levels of resistance was observed in the populations from North China. From 1996 to 1999, the changes of resistance to different insecticides were gently in Xijiang population. The tendency of resistance of H. armigera to cyhalothrin declined in Jizhou and rised in Xihua and Gaomi from 1996 to 1998. The resistance level declined in 1999 in all populations from North China because Bt cotton was commercially planted in these areas since 1998. To monocrotophos and methomyl, the tendency of resistance rised in North China from 1996 to 1999. There were similar dynamics of resistant individual frequency of H. armigera to three type insecticides in North China compared with that of the resistance level.