Impact of neonicotinoid insecticide exposure on the survival and foraging activity of honey bee, <i>Apis cerana</i>

Abstract Honey bees, essential pollinators for a wide range of important crops, are currently at risk from exposure to neonicotinoid insecticides. In this study we assessed the impact of two most commonly used neonicotinoid insecticides namely imidacloprid and thiamethoxam on honey bee, Apis cerana through controlled feeding experiment at doses of 15 ng/bee, 30 ng/bee, 60 ng/bee and 120 ng/bee. Mortality was recorded at 4, 8, 18, 24 and 48 h after exposure to insecticides. At 24 h, imidacloprid and thiamethoxam @ 60 ng/bee caused 43.75 and 72.50 % mortality, respectively. After 18 h of exposure to 120 ng/bee of imidacloprid and thiamethoxam, mortality rates reached 82.5 % and 87.5 %, respectively. Significant, dose-dependent effects of imidacloprid and thiamethoxam on bee mortality were observed over time, with the highest concentrations (120 ng/bee and 60 ng/bee) producing the most pronounced effects. Furthermore, prolonged exposure to lower doses (15 ng/bee and 30 ng/bee) induced adverse effects such as trembling and impaired coordination in bees. Overall, the differences in toxicity between imidacloprid and thiamethoxam were largely non-significant across doses and exposure durations. Field studies on foraging activity suggested that imidacloprid can negatively impact honey bee foraging behavior. Three days after exposure to sucrose spiked with imidacloprid at 0.28 mg/kg, foraging activity dropped from 62.67 bees per 10 min before treatment to 6.76 bees per 10 min. These findings emphasize the importance of addressing the harmful effects of neonicotinoids on honey bees, which impact both their behavior and survival, particularly with prolonged exposure.