Sunflower pollination in Czech Republic

The study was conducted in Central Bohemia from 1993 to 1995. Nectar secretion from 15 cultivars (hybrids) was determined and on the average 18.1 mg sugar in the nectar per 50 flowers was secreted. Significant differences in nectar secretion occurred among the cultivars. Cultivars with higher nectar production had more bee visits. Special attention was also given to gumming on flowers. The gumming intensity was influenced more by cultivar than by site. The limitation of bee foraging by gumming was not confirmed. Pollination by honey bees increased the quantity of harvested seed up to 101%, with an average of 26%. The main component in the increased yield was a larger number of harvested seeds. Honey bees foraging on sunflower did not die, and colonies moved to sunflower offered a honey harvest and had better colony development the following year.