Comparison of the Foraging Activity and Pollination Effects of Honeybees (Apis mellifera L.) and Bumblebees (Bombus terrestris L.) in Gold Kiwi (Actinidia chinensis P. ‘Haegeum’)

Abstract

Because the number of flowers of gold kiwi (Actinidia chinensis P. ‘Haegeum’) that bloom is higher than that of conventional cultivars, artificial pollination is labor intensive. To verify potential insect pollinators of the gold kiwi, in this study, we compared the kiwi pollination behavior and effects of honeybees (Apis mellifera) and bumblebees (Bombus terrestris). The efficiency of pollinating activity of a bumblebee worker was greater than that of a honeybee worker. The traffic rate of bumblebees was 1.6-fold greater than that of honeybees. In particular, the percentage of bumblebees returning to the hive with pollen was 3.1-fold greater than that of honeybees. Because the time in the flower of bumblebees was 4 s shorter than that of honeybees, assuming that the foraging time was the same, bumblebees would visit 1.6-fold more number of flowers than honeybees. However, the pollination effects of honeybees were better than those of bumblebees. The fruit set rate of honeybee-pollinated flowers was 1.3-fold higher than of bumblebee-pollinated flowers. In addition, honeybee-pollinated flowers produced 1.2-fold more number of seeds; furthermore, the fruits produced by pollination with honeybee were slightly heavier and larger than those produced by pollination with bumblebee. These results can be attributed to the fact that the number of honeybee workers per hive is 20-fold more than that of bumblebee workers per hive. Owing to the larger number of bumblebee colonies required to achieve pollination effects than that of honeybee colonies, honeybees are considered better suited for kiwi pollination because of economic constraints. However, as bumblebees have higher pollination efficiency, determining effective density could promote their use as an alternative to honeybees in kiwi pollination.