Assessment of hornet (Vespa spp.) predation on European honeybee (Apis mellifera L.) apiary at sub-tropical plain areas of Parasi district, Nepal

Abstract

The predatory hornets have become one of the major limiting factors for commercial beekeeping. So, its incidence and predation rates were investigated at two different locations of sub-tropical plain areas of Parasi district, Nepal during five major hornet active months for 2016 and 2017. Observations were carried out on five Apis mellifera L. colonies, where the number of hornet and honeybee captured by hornet were assessed at three different times of the day for three continuous minutes every fortnightly. During the study periods, five major hornet species Vespa velutina Lepeletier, V. bicolor Fab., V. basalis Smith, V. tropica (Lin.) and V. mandarina Smith were observed. The hornet incidence varied significantly between different dates and locations, while between the years it was non-significant. The incidences as well as the predation rates were low during summer and early-autumn of both year but gradually increased to its peak in the autumn season during 2016, while during 2017, the predation rate increased to its maximum during autumn season. The predation rate was observed highest during early-November (50.44%) and mid-November (46.88%) at forest and rural areas, respectively during 2016. Likewise in 2017, the maximum predation at both locations occurred during early-November (43.75 and 55.65% at rural and forest area). Both the incidence and predation by hornet was comparatively more at forest locations with some exceptions. The hornet incidence and its predation rates were positively correlated and highly significant; while it was negatively correlated with rainfall during both years. For the sustainable management approach against predatory hornets its biological, ecological and behavioral aspects on honeybee apiary have to be well understood.