Effects Of The Host Plant Alteration On The Sensitivity To Insecticides Of Cotton Aphid Aphis Gossipii Glover

The susceptibility and probably the resistance of the polyphagous insects to insecticides would vary with the host plants they fed on. A phenomenon was found that the sensitivity of the susceptible strain of cotton aphid (Aphis gossypii Glover) to pyrethroid insecticides became thousands time lower after transfered from cotton to cucumber. So a series of research, including bioassay, physiological and biochemical research and molecular biology research, had been done in order to confirm that this phenomenon is general and confident and to find out the mechanism of it. Main results are as follows:1.Cotton aphid can transfer between cotton and cucumber directly, while pomegranates and hibiscus could be the intermediate host in the transference. But the sensitivity to pyrethroid insecticides of the susceptible strain of cotton aphid transfered from cotton to cucumber was thousands time lower than the one continuously feeding on cotton and the change in sensitivity would keep up all along. What's more, when they transfered back to cotton, they were still highly insensitive to pyrethroid. On the other hand, the sensitivity to other tested insecticides, Imidacloprid,Ornethoate and Methomyl did not change obviously. The Ratio of LC50 were 2.59, 0.57 and 0.95. The change in sensitivity of the resistant strain was only 3.40-fold lower.2.After transfered from cotton to cucumber, the CarE activity of the susceptible strain of cotton aphid was raised to 2.41-fold. The ratio of Km and Vmax were 0.95 and 1.29. The GSTs activity was raised to 1.34-fold. The enzyme content increased to 1.66-fold.The MFOs activity was also raised (the ratio of synergism multiple to deltamethrin of PBO was 3.22).3.The KT50 of the cotton aphid transfered from cotton to cucumber increased significantly from 4.37min to above 120min in the Deltamethrin treatment at the dose 0.78mg/L. A base mutation (A/T) was found in theâ…¡S4~â…¡S6 segment of para sodium channel, which resulted in an amino acid mutation (Met/Leu). This amino acid mutation was the main reason of the decrease in the susceptibility to pyrethroid insecticides.