The nutritional value of Typha latifolia pollen for bees
Justin O. Schmidt, Stephen L. Buchmann And Murtadha Glaiim
Typha latifolia (Typhaceae) is a wind-pollinated plant that produces large quantities of pollen containing 14.5% starch and 17.0% protein. This starchy pollen, when fed to newly emerged adult honeybees, was nearly totally rejected when they were provided, simultaneously, with a standard mixture of bee-collected pollen from 15 other plant species. Ethyl acetate extracts from 1 g of Typha pollen were added to 20 g of an artificial diet and fed in choice tests to newly emerged worker bees. The bees preferred by over 2.5 to 1 the extract-flavoured diet over either unflavoured diet or Typha pollen, itself. In longevity tests, bees fed Typha pollen died, on average, in about 21 days compared with 25 days for sucrose-water controls, and 57 days for bees fed the standard pollen mixture. A small colony fed only Typha pollen consumed pollen rapidly at first but then consumption decreased and in 5 weeks the population declined from 5686 to 2525 adults, with only 377 new adult bees being reared. A similar colony fed a pollen mixture increased from 4024 to 4617 adults in 4 weeks and reared 2269 adults. Despite the poor colony performance on Typha pollen, the bees apparently digested the pollen as shown by an average approximate digestibility (AD) of 90.0% and average coefficient of approximate digestibility of nitrogen (CADN) of 83.6%. The amount of uric acid in faeces from Typha-fed bees was 13.1% of the total faecal nitrogen. These results suggest that Typha pollen may be toxic to bees and is avoided by them, although it is digestible. The nature of the presumed toxic activity of Typha pollen is not known but may be related to its high starch content. Overall, Typha pollen is detrimental for honeybees and would not be a good supplemental pollen for feeding to bees. However, it does contain lipid soluble phagostimulants that can be separated from the otherwise unattractive pollen.