Comparative Acute Toxicity and Safety Indices of Organophosphate Insecticides on Apis mellifera

Abstract

European honey bee (Apis mellifera L.) plays a vital role as a pollinator, contributing significantly to global ecosystems and agricultural productivity. However, their populations are increasingly threatened, primarily due to exposure to pesticides, particularly organophosphates, commonly used in agriculture for pest control. In this study, insecticides including chlorpyriphos 20 EC, dimethoate 30 EC, and profenophos 50 EC were evaluated at various concentrations (0.005–0.09%) through topical and oral application methods. Results showed significant mortality in experimental bees across all concentrations of the insecticides, with higher mortality observed in oral exposure. Mortality increased with concentration and time, with chlorpyriphos 20 EC exhibiting mortality percentages ranging from 6.67–100%, dimethoate 30 EC from 0.00–100%, and profenophos 50 EC from 8.33–100%. Toxicity assessment revealed lowest LC50 values in chlorpyriphos 20 EC (0.008) and dimethoate 30 EC (0.007) through topical and oral methods at 24 hours after treatment (HAT), respectively. Relative toxicity, extrapolated from LD50 values, was highest in chlorpyriphos 20 EC (1.62) and dimethoate 30 EC (1.85) through topical and oral methods at 24 HAT, respectively. Profenophos 50 EC exhibited the lowest safety index (0.26) through topical application and dimethoate 30 EC (0.23) through oral application at 24 HAT. Overall, the study highlights the negative impact of insecticides on A. mellifera and underscores the urgent need for a comprehensive evaluation of the risks posed by current pest control practices to honey bees and other essential pollinators.