Negative cross-resistance to chlorfenapyr in pyrethroid-resistance house flies

The purpose of the research is to evaluate the susceptibility to deltamethrin and the pro-insecticide chlorfenapyr in a field population of Musca domestica L. compared to a laboratory strain Lab UF and to clarify a possible mechanism of crossresistance to chlorfenapyr.Materials and methods. The study was carried out on the adults of the laboratory strain Lab UF and the field population Nik of the housefly M. domestica collected from a livestock farm in the Tyumen region, where pyrethroid insecticides had been used for a long time. The toxicity of the pyrethroid deltamethrin (Delcid, 4%) and the pyrrole chlorfenapyr (Pyrafen EC, 360 g/l) against insects was estimated by the no-choice feeding test. Based on the dose-mortality response, lethal concentrations of insecticides were calculated by the probit analysis and the resistance ratio was determined. To clarify the possible mechanism of cross-resistance to chlorfenapyr in the Nik population of M. domestica, the activity of the main detoxification enzymes was determined depending on sex of the insects. In addition, the presence of the kdr-mutation providing resistance to pyrethroids was assessed by the Sanger sequencing.Results and discussion. The lethal concentrations of insecticides and the resistance ratios revealed the moderate resistance to deltamethrin and high susceptibility to chlorfenapyr in the field Nik population. A statistically significant increase in the activity of monooxygenases by 2.25–4.36 times, glutathione-S-transferase by 2.02–2.18 times, acetylcholinesterase by 1.45–1.46 times and alpha-naphthyl esterase by 1.41–1.46 times was noted in females and males of the Nik population compared to these parameters of the Lab UF strain. The presence of the kdr-mutation (L1014F) in houseflies of the field population was confirmed by the Sanger sequencing, while the kdr-his mutation (L1014H) was not detected. The results obtained allow us to suggest that resistance to deltamethrin and high susceptibility to chlorfenapyr in the field population of M. domestica are caused by the L1014F mutation and the increased P450 monooxygenase activity. Negative crossresistance can be used to develop insecticidal formulations that reduce the risk of rapid development of insecticidal resistance in M. domestica L.