Foraging and Pollination Behaviour of Xylocopa Olivacea Fabricius 1787 (Hymenoptera: Apidae) on Phaseolus Vulgaris L. (Fabaceae) Flowers at Yabassi (Douala, Cameroon)

To evaluate impact of carpenter bee, Xylocopa olivacea, on pod and seed set of Phaseolus vulgaris, its foraging and pollinating activities were studied in Yabassi, for two rainy seasons (May - July 2021 and May - July 2022). Observations were made on 60 inflorescences per treatment. The treatments included unlimited floral access by all visitors, bagged flowers to deny all visits, and limited visits by X. olivacea only. In addition, all flower visitors were recorded. The carpenter bee’s seasonal rhythm of activity, its foraging behavior on flowers, its pollination efficiency, the fructification rate and the number of seeds per pod were recorded. Individuals from 11 species of insects were recorded visiting flowers of P. vulgaris in the 2 years. Xylocopa olivacea was the most frequent (58.71%), followed by Apis mellifera (15.78%) and Lipotriches collaris (10.02%). Xylocopa olivacea mainly foraged for nectar resources. The mean foraging speed was 7.62 flowers/min. Flowers visited by X. olivacea had higher fruiting rate compared with others, while those bagged had the lowest rate. In addition, seed formation was higher in X. olivacea visited flowers compared with all others. The results show that this crop experiences pollination deficit even under normal circumstances, considering that flowers visited by X. olivacea had higher yields compared with those under unlimited access by all visitors. The fruiting rate, the number of seeds/pod and the percentage of normal seeds of unprotected flowers were significantly higher than those of protected flowers from insects. X. olivacea foraging resulted in a significant boost of the fruiting rate by 29.54%, as well as the number of seeds/pod by 25.36% and the percentage of normal seeds by 15.12% in 2021 and 13.56% in 2022. Conservation of X. olivacea nests close to P. vulgaris fields could be recommended to improve pod and seed production.