[Pollinating agents and buckwheat yield (Fagopyrum esculentum Moench)]

The objective of the present work was to evaluate the influence of pollinators on buckwheat yield. A completely randomized block design was utilized with 3 treatments, each replicated 4 times: T1, with free access of pollinating agents; T2, with all pollinating agents excluded by means of an insect repellent, and T3, only with honeybees excluded by a special cage. To establish the effect of treatments on some agronomic characteristics of buckwheat (cv Mancan) observations were made 3 days before and other after harvest. Additionally, the number of insect visits was registered 3 times a day (at 10,00, 12,30 and 17,30 hrs) during January, February and March. The height of plants, the number of ramifications per plant, the number of seeds per plant and the number of seeds per inflorescence were determined before harvesting. After harvest the weight of 100 seeds, the yield and weight of 1 Hl were also determined. These data were statistically analyzed (simple and factorial ANOVA), determining means and mean squares of the simple effects as well as the interactions. It was found that number of flowers per plant, number of seeds per plant, number of seeds per inflorescence, weight of 100 seeds, yield and weight of 1 Hl were significantly (P 0,05) higher in T1 (without limitations to pollinators). The absence of honeybees (Apis melifera, Hymenoptera, Apidae) (T3) could reduce yield up to 30%. Four ssp of Hymenoptera and 2 ssp of Diptera showed the highest frequency of daily visits in all treatments and constituted 94% of all visits in T1 (without limitations to insect visits). The greatest activity of pollinators was recorded in January and February for all pollinators except honeybees whose visits peaked in February. Visits were not different during the day except for honeybees which were more active between 10 and 12,30 hrs. The exclusion of any of the main pollinators could have a negative effect on yield