155 - Creating Reference Standards for the Insect Growth Regulators Methoprene and Pyriproxyfen

Abstract: Mosquito control programs rely on precise reference benchmarks to determine whether populations are developing resistance to larvicides. For insect growth regulators such as pyriproxyfen and methoprene, however, published reference values are often inconsistent and uncertain. Additionally, the cost and complexity of maintaining susceptible reference colonies limits the global reach of resistance testing, preventing many regions from establishing reliable benchmarks and monitoring programs. To address this gap, we conducted a systematic review and meta-analysis of studies on three major vector species: Culex pipiens, Aedes aegypti, and Aedes albopictus. Our goal was to develop reference larvicide concentrations that could serve in lieu of maintaining reference colonies. We identified 72 studies that followed World Health Organization protocols and reported susceptible reference values from dose–response assays. Using a random-effects model, we calculated combined-effect benchmarks and assessed their reliability. Our analysis revealed substantial variability in the literature, with some reference populations, assumed to be fully susceptible, showing signs of resistance. These results indicate that 1) suitable reference concentrations can be established for most species–insect growth regulator pairings, reducing reliance on reference colonies, and 2) the broad range of reference values in the literature has likely contributed to an underestimation of IGR resistance on a global scale.