Assessing the pollination of kiwifruit (Actinidia chinensis var. chinensis) in the southeast United States

Due to a lack of knowledge on the pollination requirements of kiwifruit cultivars grown within the United States, farmers implement multiple pollination methods simultaneously to achieve a high fruit yield, including stocking orchards with managed bee species such as the western honey bee (Apis mellifera) and the common eastern bumble bee (Bombus impatiens), and artificially pollinating plants. To improve our understanding of the pollination of commercial kiwifruit in the southeast United States, we: 1) compared fruit set between insect pollinated and artificially pollinated flowers, and 2) assessed the contribution of A. mellifera and B. impatiens, stocked at 7 colonies/ha and 10 colonies/ha, respectively, by determining the relative abundance of kiwifruit pollen collected by foragers of each species. Although we found the corbicular pollen of A. mellifera and B. impatiens contained relative abundances of 21% and 46% kiwifruit pollen, respectively, we observed that artificially pollinated kiwifruit flowers set significantly greater numbers of fruit per flower than insect pollinated flowers. Our data suggest that insect pollinators, including A. mellifera and B. impatiens, contribute minimally to the pollination of kiwifruit in the southeastern United States under current recommended management conditions, possibly because they were drawn to competing non-kiwifruit blooms. Kiwifruit producers should put more effort into artificially pollinating their crops rather than relying on managed or wild insects for kiwifruit pollination. Future research should comparatively evaluate other methods of artificial pollination to determine their effectiveness in the pollination of kiwifruit.