Dichlorvos Resistance in the House Fly Populations, Musca domestica, of Iranian Cattle Farms

Insecticide resistance is one of the most important problems associated with the control of Musca domes tica, due to the potential of the rapid development of resistance to different chemical insecticides. The present study was carried out to evaluate dichlorvos resistance in the house fly populations collected from central regions of Iran, Isfahan Province and Chaharmahal and Bakhtiari Province, during 2017 to 2019.

Bioassays were carried out using a standard topical application method as well as a fumigation method. The Koohrang population (susceptible) with the lowest LD50 values to dichlorvos was chosen to calculate the resistance rati os (RR). Altered sensitivity of acetylcholinesterase (AChE), a target enzyme for dichlorvos, was investigated.

According to the results, very high levels of dichlorvos resistance were observed in the Mobarake population (RR= 80.25-fold by topical application and 33-fold by fumigation bioassay), and Isfahan population (RR= 107.30-fold by topical application and 43-fold by fumigation bioassay) compared to the Koohrang population. Acetylcholinesterase of the Koohrang population was the most sensitive to inhibition by dichlorvos based on the determination of median inhibitory concentration (IC50), but AChE of Mobarake and Isfahan populations were 741.93- and 343.94- fold less sen sitive to inhibition.

The insensitivity of AChE was possibly involved in dichlorvos resistance in the house fly populations.