Decreased emergence rates of adult house flies (Musca domestica; Diptera: Muscidae) due to exposure to commercially available insecticidal baits during larval development

Authors: Pitzer Jr, Jimmy; NAVARRO, JESSICA - Heritage Veterinary Hospital; Phillips, Evan

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/18/2024
Publication Date: 1/8/2025
Citation: Pitzer Jr, J.B., Navarro, J.D., Phillips, E.S. 2025. Decreased emergence rates of adult house flies (Musca domestica; Diptera: Muscidae) due to exposure to commercially available insecticidal baits during larval development. Journal of Economic Entomology. 118(1):391-396. https://doi.org/10.1093/jee/toae310.
DOI: https://doi.org/10.1093/jee/toae310

Interpretive Summary: House flies are detrimental nuisance pests due to their potential to transmit a variety of pathogens that cause disease in humans and animals alike. It is estimated that house flies cause upwards of $1 billion in economic losses to the animal agriculture industry, mostly attributed to the purchase of control products, such as insecticides. Unfortunately, house flies are extremely tolerant of chemical products, including those of newly developed formulations. Granular house fly baits are often scattered on the ground surface, attracting adult flies that consume them and succumb to the incorporated insecticide. When these baits are scattered, they may contaminate below surface substrates, potentially exposing any developing house fly larvae. It is unknown if this unintended exposure route can serve to accelerate resistance development. Therefore, a study was conducted to determine the effects of several house fly baits on developing larvae. House fly larval survival was reduced by up to 40% for two of four products evaluated. This is the first acknowledgment of a previously unrecognized pathway that may contribute to house fly insecticide resistance and accelerated product failure. Increasing our understanding of exposure pathways is an important component of mitigating insecticide resistance development in pest insect populations and provides pertinent information to guide future house fly management decisions by stakeholders.

Technical Abstract: House flies, Musca domestica L., are commonplace pests in both urban and agricultural settings. House flies demonstrate a combination of incessant nuisance behaviors and are vectors of many disease-causing organisms to humans and animals. This has resulted in a heavy desire to manage their populations. Although many house fly management tools are available, insecticide use continues to predominate as the preferred choice. One such option, insecticidal baits, are commercially available in a variety of active ingredients, encompassing several modes of action. Though they can be effective, resistance to many of the active ingredients used in bait formulations has been documented. The primary pathway for resistance evolution to bait products likely has been selection at the targeted adult stage. However, exposure at the larval stage may occur when these products are scattered on substrates, contaminating sub-surface developmental areas and ultimately, playing a selective role as well. A study was conducted to assess the potential mortality effects of insecticidal bait products on house fly larval development when applied according to the manufacturer recommended label rate. Adult house fly emergence was reduced by nearly 40% due to treatment, supporting the implication that bait-driven mortality during larval development may represent a previously unrecognized selection pathway contributing to resistance evolution against these products.