Floral visitors and the importance of honey bee on buckwheat (Fagopyrum esculentum Moench) in central Belgium

Visitors to buckwheat (Fagopyrum esculentum Moench) flowers were studied in central Belgium during 2 months (July and September) over 2 years (2001-2002). Forty-nine different insect species, belonging to 18 families, were recorded. Over both years, species from the orders Diptera and Hymenoptera were the principal visitors. Hymenoptera were mainly represented by honey bees (Apis mellifera L.; 18.5 - 51.8% of total visitors), while Diptera were represented by syrphid flies and several other families. Variation in the visitor guild occurred at the beginning and the end of both Summers, as the proportion of honey bees was significantly higher in July than in September. No variation was detected in the relative abundance of insects between years. Honey bees appeared to be the most numerous visitors. Some syrphids and other Diptera species could, however, act as co-pollinators because of their high relative frequency and activity. In experimental cages, the effectiveness of honey bee pollination was good as these insects deposited compatible pollen on a majority (90 - 93%) of flowers without any discrimination between floral morphs.