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BACKGROUND: The house fly (Musca domestica L.) is a synanthropic fly species commonly associated with confined animal facilities. House fly control relies heavily on insecticide use. Neonicotinoids are currently the most widely used class of insecticide and have been formulated into granular fly baits since 2002. Physiological resistance to imidacloprid in house flies has been observed to be unstable and decline over time without continual selection pressure, indicating that resistance has a fitness cost to individuals in the absence of exposure to insecticides. The stability of behavioral resistance to imidacloprid in the house fly has not been evaluated. In the current study, we assess the stability of physiological and behavioral resistance in house flies to imidacloprid over time. RESULTS: Physiological susceptibility to imidacloprid varied significantly among three house fly strains examined, with WT‐15 exhibiting the greatest susceptibility to imidacloprid with an LC50 and LC95 of 109.29 (95.96–124.49) μg g−1 and 1486.95 (1097.15–2015.23) μg g−1, respectively. No significant differences in survival were observed across 30 generations of a house fly strain (BRS‐1) previously selected for behavioral resistance to imidacloprid with percentage survival ranging from 93.20% at F0 in 2020 to 96.20% survival at F30 in 2022. CONCLUSION: These results have significant implications for the management of house flies exhibiting behavioral resistance in field settings. It appears that standard resistance management tactics deployed to reduce the prevalence of physiological resistance, such as rotating or temporarily discontinuing the use of specific insecticides, may not lead to reduced behavioral resistance to imidacloprid. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

BACKGROUND Toxic fly baits are commonly used for fly control in California animal operations. However, resistance development has been a problem. Comprehensive laboratory and field studies were conducted to test commercial baits (imidacloprid, methomyl, dinotefuran, spinosad) and one novel cyantraniliprole bait. A susceptible Musca domestica strain was compared with wild-type M. domestica and Fannia canicularis strains in the laboratory using choice/no-choice tests. Field visitation to baits and both short- and longer-term mortality were documented. RESULTS Susceptible Musca suffered high mortality with all baits after 3 days of choice and no-choice tests. Wild-type Musca mortality was more variable and higher in no-choice relative to choice tests. Fannia were most susceptible to spinosad > dinotefuran = cyantraniliprole > methomyl = imidacloprid. Field Musca were most attracted to spinosad > cyantraniliprole > dinotefuran > sugar > methomyl > imidacloprid. Delayed mortality from bait-fed field flies (captured and held with untreated food and water for 3 days) was ranked spinosad = cyantraniliprole > dinotefuran = methomyl > imidacloprid > sugar. CONCLUSION Behavioral resistance of M. domestica to imidacloprid and methomyl persists. Spinosad and cyantraniliprole baits (delayed mortality) performed best. Speed of action may be a factor in use and misuse of baits. © 2014 Society of Chemical Industry [ABSTRACT FROM AUTHOR]