214 - Is efficacy monitoring of IGR use in BMPs a 'pipe dream'?

Abstract: Insect growth regulators (IGRs) are a staple of larval source management (LSM) programs at the Greater Los Angeles County Vector Control District and many other vector control agencies worldwide. IGRs provide a resource- and cost-effective means of larval control and encompass several classes of insecticides, offering opportunities for product rotation aimed at resistance management. Unlike larvicidal compounds with modes of action that cause rapid mortality, IGRs act on developmental mechanisms that disrupt insect growth across life stages. In mosquitoes, this often has a significant impact on egg or pupal eclosion. Monitoring the efficacy of quick-kill larvicides by directly observing larval mortality is often relatively straightforward. However, monitoring the efficacy of IGRs requires detecting the target organisms’ inability to successfully progress through their life stages. Such follow-up checks can be time-consuming, and re-sampling treated sources to obtain pupae for observation has proven problematic often impractical. This discussion is limited to monitoring the efficacy of IGR applications in best management practices (BMPs), where BMP refers to structural controls and devices designed to regulate stormwater flow and potentially improve runoff quality. Potential sampling methods and monitoring approaches are presented, highlighting the challenges of integrating these efforts into a standard LSM program.