Determinants of nectar production in heather
With the aim of contributing to the development of decision support tools for migratory beekeepers in their planning for hive movements to heathlands in time and space, models were developed from analyses of heather flowering, nectar secretion, sugar concentration, and weight of bee hives in relation to meteorological parameters across two seasons in Denmark. The number of heather flowers was significantly lower in 2013 compared with 2012, reflecting the very long-lasting winter combined with the very dry spring period of 2013. The analyses showed that the initial number of flowers is determined by the amount of accumulated day-degree in early May, as well as the total rainfall prior to flowering and that subsequent changes in the number of flowers is governed by daily temperature and rainfall. The amount of sugar secreted per heather flower was constant throughout the observation period in 2012 and significantly higher than in 2013 when sugar secretion rate decreased in the course of the observation period. The analyses revealed that total rainfall prior to flowering, in addition to both the relative humidity and the difference between night and day temperatures in the period of secretion, is of importance for the sugar secretion rate. Fewer honey bees foraged in heather in 2013 compared with 2012, reflecting the poorer heather quality and translating directly into similar differences in weight gains of hives. Our results are useful for beekeepers in their evaluation of expected heather honey yield and thus the profitability in relocating bee colonies to heathland areas.
A Enkegaard, P Kryger, B Boelt - Journal of Apicultural Research, 2016 vol 55 p 100-106