Abstract: Susceptible toxicity baselines of Helicoverpa armigera to eleven conventional insecticides (cypermethrin, deltamethrin, cyhalothrin, fenvalerate, monocrotophos, phoxim, methyl parathion, chlorpyrifos, methomyl, thiodicarb and endosulfan) were established with leaf dipping method, and then LC₅₀ and discriminating dose were determined respectively. Resistance to cypermethrin, monocrotophos, methomyl and phoxim in H. armigera from four provinces (Jiangsu, Shandong, Henan and Anhui) was monitored by leaf dipping method and the baseline data were established. The results indicated that using discriminating dose to monitor resistant individual frequency was more rapid and simple than comparing resistance ratio at LC₅₀. Discriminating dose technique is suitable for early resistance detection and discriminating doses of the four insecticides mentioned above can be extended in resistance monitoring program of H. armigera in China.

Key words: Helicoverpa armigera, leaf dipping method, susceptible toxicity baseline, resistance monitoring