36 DISEASES OF BEES 



was then suggested that enough chlorine might be retained in the 

 treated scales of American foul brood to inhibit growth while in 

 culture. When the treated scales were washed in distilled water 

 the spores germinated surprisingly well, whereas there was no growth 

 in cultures from unwashed scales. Consequently all samples that 

 were received for testing were washed, and it was found that the 

 same thing occurred with scales that had been treated with formalde- 

 hyde, though to a less extent ; that is, formaldehyde, even in small 

 doses, appeared to delay the germination period of the spores" 

 Cases varied considerably, but, in some, germination would not take 

 place for 30 days. Therefore, before a definite diagnosis could be 

 made on any treated sample, it was deemed advisable to keep 

 cultures in incubation for 30 days before pronouncing the sample 

 sterile. 



The placing, by some of the States, of embargoes on the ship- 

 ment of bees on combs suggested to other States the imposition of 

 embargoes on honey, specifying that only honey accompanied by 

 a certificate showing that it had been produced in disease-free 

 apiaries would be allowed to enter. Whether there was a raodicum 

 of retaliation in advocating such action or whether it was just 

 misguided faith, in view of the amount of American foul brood 

 in the United States, the time was not ripe to insist upon the 

 certification of honey. The Department of Agriculture looked upon 

 honey certification as inimical to the welfare of the industry, 

 maintaining that the marketing problems did not warrant this 

 additional burden unless the certification of honey did serve its 

 avowed purpose, namely, constitute a worthwhile disease control 

 measure. Dr. A. P. Sturtevant was therefore assigned the task of 

 ascertaining the part played by commercial shipments of honey in 

 the dissemination of American foul brood. At the outset it was 

 conceivable that the spore content of honey from infected colonies 

 would vary considerably. The spore content of honey from the brood 

 chamber would most likely be different from that produced in the 

 supers. Moreover, the honey from a lightly infected colony would 

 have a smaller spore content than that from a heavily infected one. 

 These conceptions in turn presented for answer the question : What 

 constitutes the minimum infectious dose or inoculum for American 

 foul brood ? 



Dr. Sturtevant, working at Laramie, Wyoming, where colonies 

 can be completely isolated and where there are no so-called wild 

 bees, fed healthy colonies different numbers of spores suspended in 

 sugar sjrrup. Briefly, he found that the dividing line was in the 

 neighbourhood of 50 million spores fed in a liter of sugar syrup, 

 for when a smaller number was used most of the experimental 

 colonies did not develop the disease and above that point most 

 colonies did develop t5^ical American foul brood. Various subse- 

 quent tests indicated that the minimum infectious dose must be 

 close to this point. 



