House fly resistance to chlorantraniliprole: cross resistance patterns, stability and associated fitness costs

BACKGROUND The house fly, Musca domestica L. (Diptera: Muscidae) is an important public health pest that serves as a carrier for pathogens transmitting various diseases of man and animals. It is well known for rapid resistance development to insecticides applied for its chemical control. Chlorantraniliprole, an anthranilic diamide, a ryanodine receptor agonist, is a promising agent for the integrated pest management of various insect pests. To design a retrospective resistance management strategy, life history traits of the chlorantraniliprole laboratory‐selected (CTPR‐SEL) and unselected counterpart (UNSEL) sub‐populations of a field strain and their reciprocal crosses were studied. RESULTS After eight generations of consecutive selection with chlorantraniliprole, a 750‐fold resistance level when compared to a susceptible strain and a 124‐fold resistance level when compared to the UNSEL strain had developed in CTPR‐SEL. Very low cross resistance to bifenthrin but no cross resistance to spinosad and fipronil was observed in the CTPR‐SEL strain. Results of the fitness traits suggest that the CTPR‐SEL has a lower relative fitness (0.34), reduced fecundity, a decrease in eggs hatchability, lower biotic potential and net reproductive rate as compared to the UNSEL strain. Interestingly, chlorantraniliprole resistance was unstable in the CTPR‐SEL. CONCLUSIONS Fitness costs associated with chlorantraniliprole resistance suggest that the efficacy of this insecticide could be preserved for a prolonged duration of time by alternating its use with insecticides having dissimilar modes of action and no cross resistance. When cross‐resistance is absent, a sequence of two insecticides is expected to be more durable than a mixture unless the population's h 2 of resistance to the mixture is less than half of the mean of the population's h 2 of resistance to the two individual components of the mixture. Unstable chlorantraniliprole resistance could also help to sustain its efficacy by being withdrawn from usage for some period of time. © 2019 Society of Chemical Industry