Cross resistance patterns in malathion- and fenitrothion-resistant strains of the rice brown planthopper, Nilaparvata lugens Stal

The malathion- and fenitrothion-resistant (Rm and Rf) strains of the rice brown planthopper were established by successive selection with malathion and fenitrothion, respectively. The Rm strain selected with malathion for 42 generations developed 93-fold resistance to malathion, and the Rf strain selected with fenitrothion for 39 generations developed 289-fold resistance to fenitrothion. The Rm strain showed 5- to 26-fold cross resistance to naled, tetrachlorvinphos, monocrotophos, propaphos, fenthion, fenitrothion, diazinon, isoxathion, pyridaphenthion, disulfoton, dimethoate, phenthoate, mecarbam, carbaryl, propoxur, XMC and methomyl. The Rf strain showed high resistance to fenthion (271-fold), diazinon (71-fold), isoxathion (270-fold), pyridaphenthion (412-fold), EPN (177-fold), malathion (421-fold) and phenthoate (157-fold), and also showed 5- to 32-fold cross resistance to naled, dimethylvinphos, tetrachlorvinphos, monocrotophos, propaphos, disulfoton, dimethoate, mecarbam, carbaryl, MPMC, BPMC, propoxur, XMC and methomyl. In both Rm and Rf strains, no cross resistance to trichlorfon, pyrethrins and organophosphorus fungicides such as IBP and edifenphos were found.