This study addresses the urgent need to understand the ecological impacts of pesticides, focusing on the toxic effects of Dimethoate and Tau-Fluvalinate on bumblebees (Bombus terrestris), essential pollinators in agricultural and natural ecosystems. Recent declines in bee populations have highlighted the detrimental effects of agrochemicals, motivating this investigation into their impacts on bee mortality, behavior, and foraging preferences. The study finds that Dimethoate significantly increases mortality and induces erratic behaviors, while Tau-Fluvalinate exhibits lower toxicity, impacting neither bee behavior nor foraging preferences at environmentally realistic concentrations. These results underscore the importance of evaluating pesticide effects under realistic usage conditions to better guide agricultural practices and pesticide regulation. Further research is essential to explore the sub-lethal and long-term effects of these chemicals on bumblebee populations and pollination dynamics.