Synergistic toxicity of pymetrozine and cartap on mortality, Growth and reproductive performance of pheretima posthuma

Abstract:

The investigation assessed the toxicological impact of two insecticides, Pymetrozine and Cartap, on the earthworm Pheretima posthuma, focusing on mortality, biomass and reproductive potential. Experiments were conducted under controlled laboratory conditions using concentrations of 2.5%, 5%, and 7.5% of LC₅₀, with observations recorded at 12, 24, 36, and 48 days. The results revealed a clear dose dependent response across all parameters. Mortality was negligible in the control group but increased significantly under insecticide exposure, with Cartap consistently more toxic than Pymetrozine. Biomass declined progressively with concentration, indicating impaired feeding and energy metabolism, while cocoon production was markedly suppressed, reflecting disruption of reproductive physiology. The combined application of both insecticides produced the most severe outcomes, with synergistic effects leading to higher mortality, greater biomass loss, and near complete inhibition of cocoon production at the highest concentration. These findings highlight the ecological risks posed by pesticide use, particularly when compounds are applied together, as they can severely affect non-target soil organisms essential for nutrient cycling and soil fertility. The study underscores the importance of adopting sustainable pest management practices to safeguard beneficial earthworm populations and maintain soil ecosystem health.