Contribution of honey bees (Apis mellifera) pollination on sunflower yield in Tabora region, Tanzania.

Honey bees facilitate pollination during their search for nectar and pollen and in the process promote fruit and seed formation. Yet, this honey bee facilitation has not been verified for Tanzania's seed crops such as sunflower. This study aimed to determine the diversity of sunflower pollinators and the contribution of honey bees on sunflower production. Thus, a field experiment was conducted in 2019 during the rainy and dry seasons. It involved three pollination environments: (i) Plots caged with honey bees, (ii) Plots caged without honey bees, and (iii) Open field plots. Polyethylene net with 0.4 mm size were used to build cages of 4 m × 5.5 m × 8 m whereas each plot had 75 plants. The plots were laid in Randomized Complete Block Design (RCBD) each with three replicates. Insect visitors to the open field plots were observed and recorded. In open plot treatment, there were 2,509 visitors representing four orders of Hymenoptera, Diptera, Lepidoptera and Coleoptera. Honey bees were the most frequent visiting insects accounting for 69.2%. The number and weight of abortive and filled sunflower seeds between treatments for both seasons were significantly different (p ≤ 0.0001). Plots caged without insects showed significantly lower filled seed numbers and weight (p < 0.001). However, treatments for plots caged with honey bees and open field showed no significant difference in seed numbers and weight (p > 0.05). Overall insect pollination contributed up to 97.7% of the total sunflower yield. In aaddition, pollination done by honey bees contributed to 87.4% of sunflower yield. Thus, the integration of honey bees in sunflower cultivation as pollinators ensures adequate pollination and production even when used as solely pollinators. [ABSTRACT FROM AUTHOR]