Testing of Insecticide Resistance of Cotton Aphids ( Aphis gossypii Glover) in Dunhuang City,Gansu Province

During 1994～1995,the cotton aphids ( Aphis gossypii Glover) were collected from Dunhuang city, Gansu province, and were tested with twenty two kinds of insecticides by means of leaf dip method recommended by FAO (1980).The relative toxicity baseline of susceptibility for each insecticide to the aphids was established, which can be used as the relatively susceptible standard for comparision of tolerance of resistance level.Compared with the toxicity baselines of insecticides to the susceptible cotton aphids in China,it was found that the aphids were susceptible to fenvalerate and methomyl in 1994 ,had already developed middle levels of resistance to omethoate and monocrotophos(31.42 and 27.45 fold), and reached extremely high level of resistance to deltamethrin (274.39 fold),had early stage sign of resistance to biphenthrin,cyhalothrin and alphacypermethrin. In 1995, the aphids were also susceptible to fenvalerate and methomyl,was middle level of resistance to monocrotophos( 34.16 fold),achieved high level of resistance to omethoate(55.36 fold), and maintained extremely high level of resistance to deltamethrin(303.66 fold).