Foraging Activities of Honeybees (Apis mellifera L.) and Bumblebees (Bombus terrestris L.) on Passionfruit (Passiflora edulis f. edulis) Flower and their Pollination Effects

Abstract

We studied the activity and pollination effects of insect pollinators (Apis mellifera and Bombus terrestris) in passionfruit pollination to investigate the possibility of insect pollination in greenhouse-cultivated passionfruit. The climatic condition inside the greenhouse during the flowering of passionfruit, bee traffics and flower visit duration of two species were measured. In addition, the pollination effect was determined by investigating the physical characteristics of fruits according to each pollination methods. The bee traffic and foraging activity of A. mellifera were 3.6 and 7 times greater than those of B. terrestris, respectively. However, when this result was converted into a percentage to colony size, the ratio of B. terrestris was 19.1, and was 10.2 times higher than that of A. mellifera. In addition, the activity of A. mellifera was affected by the illumination level (R=0.593) and ultraviolet rays (R=0.647), but the activity of B. terrestris was less affected by light. Therefore, we considered B. terrestris to be more suitable for the pollination of passionfruit than A. mellifera. Regarding the pollination effect, there was no difference between the two insect pollinators; however, better fruit quality was observed with insect pollinators than with artificial pollination. Certain problems should be addressed when using an insect pollinator directly for the pollination of passionfruit. First, pollen robbing caused by the differences between flowering start time and bee activity start time should be considered. Second, the low pollination efficiency because of the presence of extrafloral nectaries in passionfruit should be considered. Lastly, the pollination effect caused by the colony decline because of the long duration of pollination should be factored in. If these problems are solved by controlling the activity time of the foraging bees, increasing the pollinator density by 30%, and adding or managing the bee colony, insect pollinators could be effectively used for passionfruit pollination.