Assessment of neonicotinoids toxicity and their risk to honeybee under caged and open field ecosystem

Neonicotinoids are known to affect the behavior of honeybees significantly leading to the loss of colony fitness. Most chemicals are not directly lethal to bees, but the sublethal doses of certain chemicals can adversely affect bees on olfactory learning and memory, as well as visual learning which has been reported globally. Keeping the objective of elucidating the effect two most used neonicotinoids in diverse ecosystems over a period of time, the present study was conducted to record the toxicity of imidacloprid, 17.8% SL at field application rate followed by the decreasing concentration (44, 4, 3, 2, and 1µL/mL) and clothianidin 50% WDG (125, 12, 10, 8, 6, 4, and 2 µg/mL) on honeybee. A series of experiments such as ingestion test, ingestion after starvation test, indirect contact test, topical assay test, and semi-field test followed by field test was conducted and recorded an increase in the percent mortality for the increasing concentrations of the neonicotinoids with the exposure period. It was also recorded that the lethal concentration for neonicotinoid was found significantly lower. The LC ₅₀ , LD ₅₀ , LC ₉₉ , and LD ₉₉ estimated through probit analysis recorded in similar trend along the exposure period. The Hazard Quotient (HQ) is significantly increased with the exposure period (11574 at 3 HAT and 18825 at 48 HAT) for both insecticides. This study highlighted the extremely low concentration of neonicotinoids could pose a potential toxic effect on bees and that could lead to the overall behavior of honeybee.