Flight ranges of Tetragonula “nr” pagdeni and standardization of hive density for profitable coriander production in the semi-arid region of India

Abstract

Stingless bees (Apidae: Meliponini) are the smallest of honey producing bees. The field investigation was carried out to record the effective foraging capacity of stingless bee Tetragonula “nr” pagdeni for standardizing its hive density in coriander and document the effect of bee visits on the seed quality parameters at Devihosur, Haveri, Karnataka, during 2019–2020. Four colonies were placed in the coriander’s field center, with treatments ranging from 4, 8, 12, 16, 20, 24, 28, and 32 m from the hive center. The diurnal and temporal activity of T. pagdeni and Apis florea (wild bee present in the study area) was recorded. The foraging activity of T. pagdeni and A. florea was confined to daytime from 9.00 to 17.00 h, reaching its zenith during 10.00–12.00 and 13.00–15.00 h. During the peak flowering period, the highest bee visitation (3.20/plant/minute) was noticed within the circle of 4 m from the hive. The stingless bees, T. pagdeni provided a high percentage of pollination up to a 20 m distance from the hive, showing that this is the common flying range of T. pagdeni when the same food source is accessible near the colony. Similarly, the seed quantity and quality parameters viz., seeds/umbel, seed yield, percent germination, seedling length, and vigour index were also recorded maximum values in all the treatments up to 20 m, from the hive. Whereas, the pollination success of bees decreased in successive treatments i.e., the plots at the flight range of 4 m from the hive recorded the highest seed yield (14.52 q/ha) compared to the plots at 32 m, 10.5 q/ha. Overall, the study suggests that ten colonies of T. pagdeni per acre are optimum for successful coriander seed production. The high pollination rate in coriander also depends on the unquantifiable high contribution of Apis florea in the study location