Potassium in Onion Nectar and its Probable Effect on Attractiveness of Onion Flowers to Honey Bees1

Abstract

Levels of K in nectar of onion ( Allium cepa L.) varied from 3600-13,000 ppm, about 10 times higher than that of nectar from competing flora tested. An open-pollinated amphidiploid derived from the interspecific cross A. cepa X A. fistulosum L. was the only onion with nectar K level as low as that of competing flora and it was more attractive to honey bees than was the common onion, A. cepa . Addition of K salts to sugar solutions at the rate of 1500, 3000, 4500, 6000, or 7500 ppm K clearly reduced uptake of these solutions by honey bees foraging at artificial-flower feeders. Thus, it appears that the levels of K in onion nectar are high enough to reduce the attractiveness of onion flowers to honey bees. It is suggested that pollination of onion flowers might be improved if nectar K levels can be reduced, either through a program of selective breeding or by altering cultural practices. An alternative solution might be to provide pollinators that readily accept the high K level present in onion nectar. This might be accomplished by preconditioning honey bees to accept high K levels in sugar solutions before they are moved to the onion seed fields, by developing a strain of honey bees with a preference for onion (high K) nectar, or by utilizing other species of pollinators.