Foraging and pollination activities of Xylocopa olivacea (Hymenoptera, Apidae) on Phaseolus vulgaris (Fabaceae) flowers at Dang (Ngaoundere-Cameroon)

To evaluate the impact of the carpenter bee (Xylocopa olivacea) on pod and seed sets of Phaseolus vulgaris (black seed outlets), its foraging and pollinating activities were studied in Ngaoundere, during the June-July 2009 and 2010 cropping seasons. Treatments included unlimited floral access by all visitors, bagged flowers to avoid all visits, and limited visits of X. olivacea. Observations were made on 120 flowers per treatment of which all flower visitors were recorded. The carpenter bee seasonal rhythm of activity, its foraging behaviour on flowers, and its pollination efficiency (fruiting rate, number of seeds/pod and percentage of normal or well developed seeds) were recorded. Twenty-four insect species visit P. vulgaris flowers. X. olivacea was the most frequent visitor and they intensely and exclusively foraged nectar. The foraging speed was 9.94 flowers/min. The foraging activity of X. olivacea resulted in a significant increment in fruiting rate by 48.43 and 78.18%, the number of seeds/pod by 19.38 and 18.58% and the normal seeds/pod by 15.67 and 38.25%, respectively in 2009 and 2010. Hence, conservation of X. olivacea nests close to P. vulgaris crop fields should be recommended to improve pod and seed production in the region.