02346naa a2200241 a 450000100080000000500110000800800410001910000190006024501400007926000090021952016300022865000150185865000170187365000230189065300110191365300180192465300160194265300150195870000210197370000200199470000180201477300720203214864342018-06-07       2003    bl uuuu     u00u1 u    #d1 aRIBEIRO, B. M.  aInsecticide resistance and synergism in Brazilian populations of Sitophilus zeamais (Coleopterabcurculionidae).h[electronic resource]  c2003  aInsecticide resistance to three organophosphate (chlorpyrifos-methyl,malathion and pirimiphos-methyl) and three pyrethroid (cypermethrin,deltamethrin and permethrin)insecticides was surveyed in nine .eld-collected populations of the maize weevil from six Brazilian States and contrasted with a standard susceptible population and a DDT and pyrethroid resistant population. Bioassay tests were carried out in glass vials (20 ml)impregnated with dried insecticide residue and the resistant populations were recognized by using discriminating concentrations established from LC95 s estimated for a standard susceptible population. Four .eld-collected populations had reduced susceptibility to cypermethrin (64 ?77% mortality)and to chlorpyrifos-methyl (76 ?77%mortality).All populations were susceptible to malathion and pirimiphos-methyl and only the DDT and pyrethroid resistant check showed resistance to allpyrethroids. Concentration ?mortality curves showed non-signi .cant levels of insecticide resistance in the. eld-collected populations and moderate (10 ?100-fold)to very high levels (&gt1000-fold)of resistance to pyrethroids in the DDT and pyrethroid resistant population. Results from insecticide bioassays with synergists (diethyl maleate,piperonyl butoxide,and triphenyl phosphate)suggested a major involvement of esterase as the cypermethrin resistance mechanism,while no clear result was obtained for chlorpyrifos-methyl. Synergism results provide support for target site resistance to pyrethroids in the DDT and pyrethroid resistant population used in this study.r 2002 Elsevier Science Ltd.All rights reserved.  aInseticida  aResistência  aSitophilus Zeamais  aBrasil  aOrganofosfato  aPiretroides  aSinerginuo1 aGUEDES, R. N. C.1 aOLIVEIRA, E. E.1 aSANTOS, J. P.  tJournal of Stored Products Research, Oxfordgv. 39, p. 21-31, 2003.