RFID-based assessment of sublethal effects of fenobucarb and carbendazim on honey bee homing flight

Abstract Assessing the sublethal behavioral effects of pesticides on honey bees ( Apis mellifera ) is a key component of honey bee risk assessment. In this study, we aimed to refine experimental conditions for RFID-based tracking and to evaluate the sublethal effects of fenobucarb (FNC) and carbendazim (CBZ) on honey bee homing performance. Individually tagged forager bees were exposed to sublethal doses of FNC (0.00025 and 0.0025 µg/bee) or CBZ (0.005 and 0.05 µg/bee) and monitored for 24 h. Behavioral endpoints, including the return rate, first-return time, and frequency of out-of-hive trips, were quantified via RFID detection at the hive entrance. Control and solvent-control groups showed high (> 90%) and comparable return rates, indicating high baseline homing performance and no apparent effect of solvent exposure. FNC exposure at both doses did not significantly affect homing success, median return time, or frequency of out-of-hive trips relative to solvent exposure. At the lower dose, CBZ exposure significantly reduced the return rate; however, this effect was not observed at the higher dose and was not accompanied by changes in median return time or frequency of out-of-hive trips, suggesting the absence of a consistent or dose-dependent behavioral response. Considering the overall pattern across behavioral endpoints, no consistent adverse effects on homing-related behavior were observed for either substance under the study conditions. Overall, the refined RFID methodology provided consistent and reliable measurements of sublethal behavioral performance in honey bees.