The foraging activity of honey bees Apis mellifera and non-Apis bees on hybrid sunflowers (Helianthus annuus) and its influence on cross-pollination and seed set

The repercussions of concurrent foraging by honey bee (Apis mellifera) and non-Apis bee populations on cross-pollination and seed set in hybrid sunflowers (Helianthus annuus) was investigated. The amount of sunflower pollen on the bodies of honey bees foraging in rows of male-sterile (MS) sunflowers was positively correlated with the size of the non-Apis bee population. The combined population of non-Apis bees and honey bees foraging on male-fertile (MF) and MS sunflowers also was positively correlated to seed set in MS rows. There were more honey bees than non-Apis bees foraging in MF and MS rows, but there was no evidence of competition for resources between the two populations. The size of the honey bee population was positively correlated to the area of open flowers on sunflower capitula, while the non-Apis population remained relatively constant throughout bloom. Results from this study indicate that a combined honey bee and non-Apis bee population might result in better pollination of hybrid sunflowers than either population alone.