Effect of Workers Density on Insect Pest Incidence and Colony Development of Bumblebees, Bombus terrestris (L.) (Hymenoptera: Apidae)

Abstract

Insect pollination improves essential nutrients and qualities of pollinating plants. Approximately 90% of flowering plants and 35% of crops require insect pollination. Bees play a vital role in pollination in natural and agricultural systems. Managed bees have extensively been used for pollination. Unfortunately, the native bee population has been waning globally. Commercial bee-rearing experiences different rearing problems i.e. food, environment, and spatial conditions within colonies. In this research, the impact of different densities of workers within colonies of Bombus terrestris L. was observed on colony development and pest incidence. Different worker densities i.e. 60-70, 80-90,110-120 and 140-150, respectively, were maintained under controlled laboratory conditions. The results indicated that emergence of workers was higher in less dense colonies (60-70 workers) as compared with highly dense colonies (140-150 workers). Maximum drone emergence was observed in colonies having 80-90 workers as compared with highly denser colonies. The numbers of young queens were the highest in denser colonies. Mortality percentage of bumblebees and insect pest incidence were also higher in denser colonies. Therefore, the colony with 80-90 workers can be used as an indicator for bumblebee-rearing on a commercial scale in the laboratory.