THE SIZE AND DISTRIBUTION OF THE HONEY-BEE (APIS-MELLIFERA L) CROSS-POLLINATING POPULATION ON MALE-STERILE SUNFLOWERS (HELIANTHUS-ANNUUS L)

The size of the honey bee (Apis mellifera) population carrying sunflow er (Helianthus annuus) pollen on their bodies while foraging on male-s terile (MS) plants was recorded. When equal numbers of MS and male-fer tile (MF) rows were planted, all foragers had some sunflower pollen on their bodies, and the amount did not differ among MS rows at various distances from MF plants. When MS rows outnumbered MF by 3 to 1, 97.7% of the honey bees foraging on the MS row farthest from the MF plants had sunflower pollen on their bodies, but the amount was significantly less than on foragers on MS rows closer to MF plants. Seed set on MS rows adjacent to MFs did not differ from that on MF plants, but set de creased in MS rows further away. The percentage of pollen-collecting h oney bees moving from MF to MS rows indicates one means by which the c ross-pollinating honey bee population can be created, but these bees r epresented only 6.5-12.8% of all foragers. Pollen-free honey bees eith er released in hives located near sunflower fields or pinned at the hi ve entrances obtained sunflower pollen grains on their bodies, but the amount was much less when MS rows outnumbered MF by 3 to 1. Pollen tr ansfer in the hive may be a component in the creation of the cross-pol linating honey bee population on MS sunflowers, but the impact may var y with MF: MS row ratios and the amount of sunflower pollen entering t he hive.