STUDIES ON CULTIVAR-INDUCED CHANGES IN INSECTICIDE SUSCEPTIBILITY AND ITS RELATED ENZYME ACTIVITIES OF THE WHITE BACKED PLANTHOPPER, SOGATELLA FURCIFERA (HORVTH) (HOMOPTERA:DELPHACIDAE)

The susceptibility of Sogatella furcifera female adults on N22 to malathion increased as feeding time prolonged, while the day change of susceptibility to isoprocarb showed a inverse tendency. The activities of esterase and carboxylesterase were induced significantly after on N22 for one day, and then declined. The non susceptible level of adults to insecticides and enzyme activities seemed to be heightened after feeding on ASD7, a variety resistant to Nilaparvata lugens. The total phenol content in rice leaf sheath was the highest in N22, and could be regarded as one of the factors, which caused chages in susceptibility of S. furcifera to insecticide after feeding different rice varieties. It was recommended that suitable insecticides and planthopper resistant varieties should be coordinately used in practice so that they contribute more effects respectively.