Pollination and yield responses of cowpea (Vigna unguiculata L. Walp.) to the foraging activity of Apis mellifera adansonii (Hymenoptera: Apidae) at Ngaoundere (Cameroon)

To determine the apicultural value of Vigna unguiculata (L.) Walp. (Fabaceae) and evaluate the Apis mellifera adansonii Latreille (Hymenoptera: Apidae) activity on its pod and seed yields, the bee foraging and pollinating activities were studied in Ngaoundere. The experiment was carried out within the University of Ngaoundere Campus on 210 flowers differentiated in two lots, based on the protection/or not of plant inflorescences against insect visits. The bee's seasonal rhythm of activity, its foraging behaviour on flowers, the fructification rate, the number and dry weight of seeds/pod, the percentage of normal seeds/pod, and the pod length were evaluated. Results show that A. m. adansonii foraged on plants throughout the whole blooming period. Worker bees intensively and preferably harvested nectar. The greatest mean number of workers foraging simultaneously was 500 per 1000 flowers. The mean foraging speed was 8.67 flowers/min. These findings allow the classification of V. unguiculata as a highly nectariferous bee plant. The number and dry weight of seed/pod, the pod length and the percentage of normal seeds/pod from unprotected flowers were significantly higher than those of flowers protected from insects. The fructification rates were 62 and 48%, while the percentages of healthly seeds were 97.61 and 76.17%, respectively in unprotected and protected inflorescences. The installation of A. m. adansonii colonies close to V. unguiculata field could be recommended to improve its pods and seeds production in the region.