Sept, 1,1932 Commercial Honey and Spread qf American Foulbrood 261 



After a considerable number of counts had been taken in making 

 up several stock suspensions of spores, counting was eliminated and 

 the spore content of the stock suspensions was standardized according 

 to the method described by Gates {11, p. 114), as follows: "The 

 opacity of a bacterial suspension is measured by the length of a col- 

 umn of the suspension required to cause the disappearance of a wire 

 loop." An instrument known as a suspensiometer was used for this 

 purpose. The use of this method saved considerable time and labor 

 without appreciably affecting the precision of the counts. One liter 

 of a 50 per cent solution of sugar in water was used as the standard 

 quantity of inoculated sirup fed to each experimental colony. A 

 series of dilutions of the original stock suspension containing 5,000,- 

 000,000 spores was made by adding different quantities of the spore 

 suspension to 1 liter of sugar sirup. In this way the approximate 

 total number of spores in each liter of sugar sirup to be fed to colonies 

 of bees was known. 



Method op Inoculating Colonies 



In 1926 at Somerset, Md., the sugar sirup containing the various 

 dilutions of spores was fed to the colonies by means of galvanized-iron 

 troughs that were hung inside the hives after two combs had been 

 removed. In these troughs sterile excelsior was placed for the bees 

 to walk on in order to prevent them from drowning. This method 

 was found unsatisfactory, however. At Laramie, Wyo., the sugar 

 sirup containing the spores was first placed in Boardman feeders, but 

 owing to the danger of robbing at the entrance of the hives, the 

 method finally used was to invert the jars in holes bored in the hive 

 covers. In this way any leakage into the hives was cleaned up by the 

 bees without danger of causing robbing. To prevent the jars from 

 being broken or knocked over, box covers were placed over them and 

 fastened to the hive covers. Each colony was usually inoculated only 

 once with an individual dilution of spores. Duplicate colonies were 

 inoculated with each dilution of spores. Uninoculated check colonies 

 were placed among those that were inoculated. 



PRIMARY OBSERVATIONS 



Observations of the condition of the brood were made at least once 

 a week, and sometimes oftener, after the colony was given the liter of 

 inoculated sirup. In 1926 at Somerset, Md., as soon as diseased 

 larvae appeared in a colony, the colony was killed and at once re- 

 moved from the apiary. Because of the isolated location near Lara- 

 mie, Wyo., the colonies were left until the end of the brood-rearing 

 season, when fiaal observations were made. 



The results of the spore-feeding experiments are shown in Table 1. 



