Foraging and pollination activity of Apis mellifera adansonii Latreille (Hymenoptera: Apidae) on flowers of Allium cepa L. (Liliaceae) at Maroua, Cameroon

Abstract To evaluate the impact of Apis mellifera adansonii (Hymenoptera: Apoïdae) on fruit and seed of Allium cepa its foraging and pollinating activities were studied in Maroua, from November 2010 to April 2011 and 2012. Treatments included unlimited floral access by all visitors, bagged flowers to avoid all visits and limited visits of A. m. adansonii. Observations were made on 120 flowers per treatment. Flowers of Al. cepa were prospected four days per month, between 07.00 and 18.00 h, for recording of the nectar and/or pollen foraging behaviour of each pollinator. The worker bee's seasonal rhythm of activity, its pollination efficiency, the fruiting rate, the number of seeds per fruit and the percentage of seeds well developed were recorded. Results show that honey bee intensely and preferably foraged for nectar, almost throughout the day, with a peak between 8 and 9 am. The foraging speed was 47.12 ± 7.19 flowers per minute. Individuals from 22 species of insects were recorded on flowers of Al. cepa. A. m. adansonii was the most frequent with 40.62% and 51.48% of visits in 2010 and 2011 respectively. Its foraging resulted in a significant increase in the fruiting rate by 62.5% in 2010 and 53.8% in 2011, as well as the number of seeds per fruit by 86.44 in 2010 and 89.77% in 2011, and the percentage of normal seeds by 63.26 in 2010 and 59.78% in 2011. The use of A. m. adansonii colonies is suggested to increase fruits, seeds and honey production.