Impact of managed stingless bee and western honey bee colonies on native pollinators and yield of watermelon: A comparative study

Abstract

Watermelon (Citrullus lanatus) is an important crop cultivated in India and other warmer regions of the world. The crop is dependent on insect pollinators for its fruit set. However, information about pollination ecology in Indian states remains undetermined. We used a replicated field-scale experiment to identify the native pollinators and their foraging behaviour, including abundance, visitation rate, duration of visit, and pollination efficiency. We compared treatments with open-pollinated, hand-pollinated and the addition of two managed pollinator species to estimate the yield enhancement potential of managed stingless bees and western honey bees and their impact on native pollinator species. We found that ants, bees, butterflies, beetles, and wasps visited the flowers either for nectar, pollen, and/or floral tissue. Regarding the ‘pollinator importance’ value of the visitors, Halictus acrocephalus and Lasioglossum funebre were the most effective native pollinators. Despite their contribution, the plants showed a significant pollination deficit in the open-pollinated system which can be overcome by supplementary pollination services through the management of western honey bees (Apis mellifera) and/or stingless bees (Tetragonula iridipennis). However, the application of A. mellifera colonies greatly reduces the abundance, visitation rate and foraging time (amount of time spent per visit on a flower) of native pollinators. Hence, the utilization of managed stingless bee colonies for pollination services is more suitable and has a lesser impact on native pollinator species, which may lead to sustainable agricultural practices.