Assessment of pyriproxyfen 0.5% (juvenile hormone analog) against mosquito (Diptera: Culicidae) larvae: a multiscale study from laboratory to field

Vector control strategies increasingly focus on nonconventional chemicals with high insecticidal efficacy, persistence, and low toxicity to nontarget organisms. The present multiphase study, conducted in laboratory, semifield, and field conditions in Jaipur, Rajasthan, India, evaluated the efficacy of pyriproxyfen (0.5%) (juvenile hormone analog) in controlling mosquito emergence. Laboratory bioassays demonstrated significant susceptibility of Culex tritaeniorhynchus Giles, 1901 (Diptera: Culicidae) larvae, with the first and second instars exhibiting 100% mortality at 1 ppm and third and fourth instars showing emergence inhibition (IE) of 86.11% and 65.28%, respectively. Probit analysis determined lower LC₅₀, LC₉₀, and LC₉₉.₉ values for the first instar larvae as 0.18 ppm, 0.38 ppm, and 1.05 ppm, respectively, confirming the higher susceptibility of early instars (p < 0.05). Semifield trials with Aedes sp. and Anopheles sp. larvae showed variable IE%, ranging from 25–50% in some sites to >50% in others, reflecting the impact of prolonged exposure (p < 0.001, F = 10.32). Daily water replenishment in field trials reduced pyriproxyfen’s efficacy compared to laboratory trials. However, it exhibited a relatively higher IE% in Amargarh (5.21–70.20%, p < 0.001, F = 25.72) compared to Jhalana (9.9–64.27%, p < 0.001, F = 8.28) suggesting a potential role of pyriproxyfen (0.5%) in long-term mosquito control strategies. After treatment, water chemistry analysis revealed a progressive shift toward alkalinity (pH > 6.9) with fluctuating levels of TDS and EC, correlated with reduced larval densities. The results further validate pyriproxyfen’s effectiveness as a potent larvicide, particularly against early instars, reinforcing its potential role in integrated vector management (IVM) programs.