26 BULLETIN 431, U. S. DEPARTMENT OF AGRICULTURE. 



and Switzerland (Burri, 1906). Beuhne (19.13) reports its presence 

 in Australia, and Bahr (1915) has encountered a brood disorder 

 among bees in Denmark which he finds is neither of the foul broods. 

 He had examined 10 samples of it but had not studied it further. 

 He says it may be sacbrood. 



About 400 cases of sacbrood have been diagnosed by Dr. A. H. 

 McCray and the writer among the samples of brood received for 

 examination at the Bureau of Entomology. A few of these were 

 obtained from Canada. Whether the disease occurs in tropical 

 climates or the coldest climates in which bees are kept has not yet 

 been completely established. 



The mountains and coast plain of the eastern United States, the 

 plains of the Mississippi Valley and the mountains, plateaus, and coast 

 plain of the western portion of the country have contributed to the 

 number of samples examined. It occurs in the South and the North. 



Its occurrence in such widely different localities is proof that sac- 

 brood is of such a nature that it can appear under widely different 

 climatic conditions. The relative frequency of the disease, further- 

 more, is not materially different in the different sections of the country. 

 It must be said, however, that the extent, if any, to which the dis- 

 ease is affected by climate has not yet been determined. 



The practical import of these observations regarding climate, of 

 particular interest here, is that the presence of sacbrood in any region 

 can not be attributed entirely to the prevailing climatic conditions. 



Season. — It has long been known that sacbrood appears most often 

 and in the greatest severity during the spring of the year. As is 

 shown by the results obtained in the diagnosis of it in the laboratory, 

 the disease may appear at any season of the year at which brood is 

 being reared. In the inoculation experiments sacbrood has been 

 produced with ease from early spring to October 21. While it is thus 

 shown that the brood is susceptible to sacbrood at all seasons, 

 various factors together cause the disease to occur with greater 

 frequency during the spring. 



Food. — Before it was known that sacbrood is an infectious disease 

 the quantity or quality of food was not infrequently mentioned by 

 beekeepers as being the cause of the disease. Since a filterable virus 

 has been shown to be the exciting cause of the disease, it is left to be 

 considered whether food is a predisposing cause. The distribution 

 of the disease mentioned above, under the heading "Climate," here 

 again serves a useful purpose. Since it occurs in such a wide range 

 of localities, wherein the food and water used by the bees vary as 

 greatly almost as is possible in the United States, the conclusion may 

 be drawn that its occurrence is not dependent upon food of any 

 restricted character. Furthermore, sacbrood is found in colonies 

 having an abundant supply of food, as well as in colonies having a 



