Study of the effect of the plant extract of <i>Tribulus terrestris</i> L. on the foraging activity of bees (summer flight activity)

Abstract Honey bee (Apis mellifera L.) colony productivity and foraging activity are influenced by both external factors, such as climatic conditions and nectar availability, and internal factors, including colony strength and queen fertility. While plant-based supplements have been studied for their effects on colony health and productivity, the impact of Tribulus terrestris L. on summer flight activity remains unknown. This study evaluated the effect of T. terrestris extract on honey bee foraging behavior over two consecutive seasons (2024–2025) in three Bulgarian apiaries. Three groups were established: a control fed with inverted sugar syrup, an experimental group supplemented with T. terrestris extract, and a second experimental group receiving the Startovit mineral-vitamin stimulant. Flight activity was measured by counting bees departing each hive during three-minute intervals. Results showed that T. terrestris supplementation significantly increased summer flight activity compared to the control and “Startovit” groups, with the highest increases observed in 2024. These findings provide the first experimental evidence that T. terrestris extract can enhance honey bee foraging behavior, suggesting its potential as a natural, non-hormonal stimulant to improve colony performance and resource utilization.