Monitoring insecticide resistance, determining genetics and cross-resistance in house fly, Musca domestica L. (Diptera: Muscidae), from poultry farms of Punjab, Pakistan

House flies, Musca domestica L. (Diptera: Muscidae), are pests of poultry and have ability to develop resistance against different insecticides. This study was conducted to assess the resistance status of M. domestica to pyrethroid, organophosphate and novel chemistry insecticides from poultry facilities in Punjab, Pakistan. Five adult M. domestica populations were studied for their resistance status to selected conventional and novel chemistry insecticides. For four pyrethroids, the range of resistance ratios was 14-55 fold for cypermethrin, 11-45 fold for bifenthrin, 0.84-4.06 fold for deltamethrin and 4.42-24.00 fold for lambda-cyhalothrin when compared with a susceptible population. Very low levels of resistance were found to deltamethrin compared to the other pyrethroids. For the three organophosphate insecticides, the range of resistance ratios was 1.70-16.00 fold for profenofos, 7.50-60.00 fold for chlorpyrifos and 4.37-53.00 for triazophos. Very low levels of resistance were found to profenofos compared to the other insecticides. For eight novel chemistry insecticides, the range of resistance ratio was 1.20-16.00-fold for fipronil, 3.73-7.16-fold for spinosad, 3.06-23.00-fold for indoxacarb, 0.96-5.88-fold for abamectin, 0.56-3.07-fold for emamectin benzoate, 4.9-16-fold for acetamiprid, 2-14-fold for imidacloprid and 9.7-35-fold for nitenpyram. For four IGRs, the range of resistance ratio was 0.3-6.6-fold for pyriproxyfen, 0.8-18-fold for cyromazine, 1-22-fold for lufenuron and 1-14-fold for methoxyfenozide. Musca domestica are managed worldwide using a variety of insecticides. However extensive and injudicious insecticide use has led to the development of resistance. Insecticide mixtures can increase efficacy of the product and/or delay resistance development, thus making them a useful tool for pest control. Mixtures of emamectin benzoate, spinosad or nitenpyram with either lambda-cyhalothrin or profenofos were assessed against M. domestica collected from poultry farms, as well as assessing their activities alone. The combination indices for lambda-cyhalothrin/emamectin benzoate and lambda-cyhalothrin/spinosad mixtures were significantly greater than 1, indicating an antagonistic effect. In contrast, the indices for all tested ratios of lambda-cyhalothrin/nitenpyram were significantly lower than 1, suggesting a synergistic effect. For mixtures containing profenofos, the indices varied significantly, for example, synergism was observed with a 1:1 mixture containing emamectin benzoate, but antagonism occurred when a higher proportion of the latter insecticide was used. Conversely, synergism in mixtures of profenofos and nitenpyram was only observed using lower proportions of the latter insecticide. Lambda-cyhalothrin, a pyrethroid insecticide, has been used frequently for the control of M. domestica worldwide including Pakistan. To assess the resistance risk and design a resistance management strategy, a M. domestica population was exposed to lambda-cyhalothrin in laboratory to assess inheritance and heritability, and cross resistance to other insecticides, including different chemical classes. After 11 generations of selection, the population developed 113.57-fold resistance to lambda-cyhalothrin compared to the susceptible population. There was no cross resistance to bifenthrin and methomyl, but very low cross resistance to abamectin and indoxacarb in the lambda-cyhalothrin selected population compared to the field population. Synergism bioassay with piperonyl butoxide (PBO) and S,S,S,-tributylphosphorotrithioate (DEF) indicated that lambda-cyhalothrin resistance was associated with microsomal oxidases and esterases. The LC50 values of the F1 (Lambda-SEL ? ×Susceptible ? ) and F'1 (Lambda-SEL ? × Susceptible ? ) populations were not significantly different and dominance (DLC) values were 0.68 and 0.62. The resistance to lambda-cyhalothrin was completely recessive (DML=0.00) at highest dose and completely dominant at lowest dose (DML=0.95). The monogenic model of inheritance showed that lambda-cyhalothrin resistance was controlled by multiple factors. The heritability values were 0.20, 0.04, 0.003, 0.07 and 0.08 for lambda-cyhalothrin, bifenthrin, methomyl, indoxacarb and abamectin resistance, respectively. Fipronil is a GABA gated chloride channel inhibiting insecticide, has been commonly used for the management of different pests including M. domestica throughout the world. A field collected strain of M. domestica was selected with fipronil for continuous 11 generations to assess cross-resistance, genetics and realized heritability for designing a resistance management strategy. Bioassay results at G12 showed that the fipronil selected strain developed a resistance ratio of 140-fold compared to the susceptible strain. Synergism bioassay with piperonyl butoxide (PBO) and S,S,S,-tributylphosphorotrithioate (DEF) indicated that fipronil resistance was associated with microsomal oxidase and also esterase. Reciprocal crosses between resistant and susceptible strains showed an autosomal and incompletely dominant resistance to fipronil. The LC50 values of the F1 and F? 1 strains were not significantly different and dominance values were 0.74 and 0.64, respectively. The resistance to fipronil was completely recessive (DML=0.00) at highest dose and incompletely dominant at lowest dose (DML=0.87). The monogenic resistance based on chi-square goodness of fit test and calculation of the minimum number of segregating genes showed that resistance to fipronil is controlled by multiple genes. The fipronil resistance strain confirmed very low cross-resistance to emamectin benzoate and spinosad whilst no cross-resistance to chlorpyrifos and acetamiprid when compared to that of the field population. The heritability values were 0.112, 0.075, 0.084, 0.008 and 0.052 for fipronil, emamectin benzoate, spinosad, acetamiprid and chlorpyrifos, respectively. The populations of M. domestica were collected from poultry facility located at Khanewal, Punjab, Pakistan in three seasons (July, November and March) to investigate the fluctuations in resistance to conventional (organophosphate, pyrethroid) and novel chemistry insecticides. All M. domestica populations showed varying degrees of susceptibility for all tested insecticides. Comparisons between populations at different seasons showed a significant fluctuation in susceptibility to organophosphate, pyrethroid and novel chemistries. Highest resistant levels were found for organophosphate when compared with pyrethroid and novel chemistry insecticides. All conventional and novel chemistry insecticides were significantly correlated with each other. Regular insecticide resistance monitoring and integrated management plans on poultry farms are required to prevent resistance development, field control failures and environmental pollution. Rotation of insecticides with different modes of action showing no or very low resistance, may prevent insecticide resistance in M. domestica. The present results also suggest that ideal insecticide mixtures must be empirically determined and alternative strategies like mosaics, rotations and cultural control should be considered for the management of M. domestica. The results of our study also concluded that M. domestica has the potential to develop multiple insecticide resistances following continued selection pressure with lambda-cyhalothrin and fipronil. These findings would be helpful in assisting the development of resistance management strategies and improve the management of M. domestica. The rotation of insecticides showing lack of cross-resistance and instability of resistance could be the part of an effective resistance management strategy.