Organophosphorus resistance in the sheep blowfly, Lucilia cuprina (Wiedemann) (Diptera: Calliphoridae): a genetic study incorporating synergists

Abstract

AbstractPre-treatment of females of Lucilia cuprina (Wied.) with the synergist piperonyl butoxide increased the resistance factors of an organophosphorus-resistant strain Q to four organophosphates in comparison to the susceptible strain LS. However, pre-treatment with S,S,S-tributylphosphorothrithioate (TBPT) reduced the resistance factors of Q to three organophosphorus insecticides. As TBPT is an esterase inhibitor, it is suggested that esterases contribute to resistance in the Q strain. Resistance to diazinon in the Q strain is due to a single, partially-dominant gene on chromosome 4. By the use of the backcross and discriminating dose technique, resistance to parathion, fenitrothion, chlorfenvinphos and fenitro-oxon (dimethyl 3-methyl-4-nitrophenyl phosphate) (the latter two were synergised by piperonyl butoxide to obtain a genetically discriminating dose) was also shown to be controlled by a single, partially-dominant gene on chromosome 4. It is concluded that this gene confers resistance to organophosphorus compounds in L. cuprina, probably by providing an esterase with enhanced ability to degrade organophosphates.