BULLETIN OF THE 



i 



No. 92 



Contribution from the Bureau of Entomology, L. O. Howard, Chief. 

 May 15, 1914. 



DESTRUCTION OF GERMS OF INFECTIOUS BEE 

 DISEASES BY HEATING. 



By G. F- White, M. D., Ph. D., Expert, Engagedin the Investigation of Bee Diseases. 



INTRODUCTION. 



To reduce the losses due to bee diseases beekeepers have often 

 employed heat in one form or another. The direct flame has been 

 used in scorching or burning the inside of hives that have housed 

 infected colonies. Before being fed back to bees honey is often 

 heated for the purpose of destroying the germs of bee diseases, should 

 any be present. Heat is used in the rendering of wax and in the mak- 

 ing of comb foundation. It is natural and very appropriate, there- 

 fore, that beekeepers should inquire about the amount of heating 

 that is necessary to destroy the germs that produce diseases among 

 bees. 



As no work had been done to determine the facts relative to this 

 question with any degree of accuracy, the writer has performed during 

 the last two years a number of experiments for the purpose of ascer- 

 taining them. Of these experiments 55 are summarized in the three 

 tables included in this paper. It may be of interest to beekeepers to 

 know in a general way how these experiments were made. A brief 

 description of the methods used will serve also to make the tables 

 more readily understood. An aqueous suspension of larvae sick or 

 dead of the disease is made and placed in a small glass tube. This 

 tube is immersed in water of the temperature desired in the heating. 

 After the germ-containing material is heated in this way it must be 

 tested to determine whether or not the germs have been destroyed. 

 In the case of American foul brood this can be done by inoculating a 

 suitable artificial medium with the heated material and observing the 

 presence or absence of growth of Bacillus larvse, the germ of this dis- 

 ease. As there is no artificial medium now known suitable for culti- 

 vating the infecting agent of either European foul brood, sacbrood, 



Note.— This paper is of Interest to beekeepers in all parts of the United States; it was read before the 

 New York State Beekeepers' Association, February 10, 1914, at Ithaca, N. Y. 

 35960°— 14 



