Reduction of Bacillus Larvae Spores in Liquid Food of Honey Bees by Action of the Honey Stopper, and Its Relation to the Development of American Foulbrood

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Abstract
It has been known for a long time that particles such as pollen grains, are removed from suspension in a liquid in the honey stomach of the honey bee Apis mellifera, by the valve-like structure in the anterior end of the proventriculus, known as the honey stopper. It has been shown in relatively recent years that particles such as Aspergillus mold spores and even the much smaller spores of Bacillus larvae, the cause of American foulbrood, are removed from liquids containing such spores fed to bees, by this mechanism. Expts. started in 1945 and continued in 1947 and 1949 descr. in this paper, were conducted in an affort to demonstrate the extent to which colonies of bees may protect themselves by this spore removal action. More or less of a relationship was seen between the spore removal by the bees of various test colonies and such factors as the initial spore content of the liquid fed to the bees, the current status of disease in the test colonies, the history of resistance shown by the different strains of bees, and the degree of resistance shown by the individual colonies. Bees from 9 colonies known to be highly resistant to American foulbrood, removed more spores from a suspension in sugar sirup (avg. 79%), than did bees from 8 colonies that had allowed more or less disease to develop (avg. 59%) at one time or another during the active season. This reduction of spores probably is important in protecting colonies from American foulbrood only when it functions at the time the contaminated liquid food first becomes available to the colony. It probably does not materially affect the spread of disease within the colony after the disease has become established. The development of the infection also depends on the spore content of the contaminated honey brought into the hive by the bees. Since the max. avg. spore removal was found to be only 79%, the stored food would still be a potential source of infection unless the spore content was reduced below the min. dose capable of producing disease in the colony.

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