Original article Agronomy Activité de butinage et de pollinisation de Apis mellifera adansonii Latreille (Hymenoptera: Apidae) sur les fleurs de Helianthus annuus (Asteraceae) à Ngaoundéré (Cameroun)

To determine the apicultural value of Helianthus annuus L. (Asteraceae) and to evaluate Apis mellifera adansonii Latreille (Hymenoptera: Apidae) impact on seeds yields of H. annuus species in Cameroon, bee foraging and pollination activities were observed in the area of Ngaoundere. From September to November, in 2004 and 2006 respectively, 66 and 104 capitula divided in two lots differentiated according to the presence or absence of the capitula protection regarding insect visits were labelled. The honey bee’s daily rhythm of activity, its foraging behaviour on flowers and the percentage of fruits with seeds were evaluated. Results showed that A. m. adansonii foraged on sunflower all day long and throughout the whole blooming period of this plant. Worker bees intensely harvested pollen and nectar. The greatest number of workers foraging simultaneously was 14 per capitula in 2004 and 15 per capitula in 2006. The mean foraging speed was 24.70 florets/min in 2004 and 24.04 florets/min in 2006. Data obtained allow the classification of H. annuus as a highly nectariferous and highly polliniferous bee plant. The percentage of fruits with full seeds of unprotected capitula was significantly higher than that of capitula protected from insects. A. m. adansonii contributed 62.07 % and 74.70 to the seeds yields in 2004 and 2006 respectively. The installation of A. m. adansonii colonies in the plantation of sunflower should be recommended to increase honey, pollen and seeds production.