Pollination by Xylocopa olivacea Fabricius 1871 (Hymenoptera: Apidae) and potential benefits on Vigna unguiculata (L.) Walp. 1843 (Fabaceae) production in Djoumassi (North Region, Cameroon)

The investigation aimed to assess the impact of Xylocopa olivacea on Vigna unguiculata yields, and its foraging and pollinating activities were studied at Djoumassi from October 30th to November 04th in 2018 and from 04 to 10th October in 2019. A total of 540 flowers were observed, divided into four treatments. Two treatments were differentiated based on the presence or absence of flower protection against insect visits. The third treatment consisted of protected and opened flowers, allowing X. olivacea visits, while the fourth treatment involved opened flowers that were later closed without any visit. The daily rhythm of the bee's activity, as well as its foraging and pollination activities, was evaluated. Results indicated that X. olivacea intensely and exclusively collected nectar from V. unguiculata flowers. Its pollination efficiency increased the podding rate by 19.44 and 27.01%, the mean number of seeds per pod by 33.42 and 29.38%, and the percentage of normal seeds by 30.12 and 25.43% in 2018 and 2019, respectively. Therefore, it is recommended to establish and increase nests of X. olivacea near V. unguiculata fields to enhance pod and seed yields.