8 BULLETIN 92, U. S. DEPARTMENT OF AGRICULTURE. 



SUMMARY AND GENERAL REMARKS. 



The results of these experiments show that when they are main- 

 tained for 10 minutes the minimum temperatures that can be used 

 for destroying the germs of the four bee diseases now known to be 

 infectious are as follows : 



( 1) The minimum temperature for European foul brood lies some- 

 where between 60° C. (140° F.) and 65° C. (149° F.), being approxi- 

 mately 63° C. (145.4° F.). 



(2) The minimum temperature for American foul brood lies some- 

 where between 90° C. (194° F.) and 100° C. (212°) F., being probably 

 less than 98° C. (208.4° F.). 



(3) The minimum temperature for sacbrood lies somewhere between 

 55° C. (131° F.) and 60° C. (140° F.), being approximately 58° C. 

 (136.4° F.). 



(4) The min imum temperature for Nosema disease lies between 

 55° C. (131° F.) and 60° C. (140° F.), being approximately 57° C. 

 (134.6° F.). 



It will be noted, therefore, that 63° C. (145.4° F.) for European 

 foul brood, 98° C. (208.4° F.) for American foul brood, 58° C. (136.4° F.) 

 for sacbrood, and 57° C. (134.6° F.) for Nosema disease are the ap- 

 proximate mrnimum temperatures at which the germs of these dis- 

 eases, respectively, are destroyed. Since there are varying factors 

 in experiments of this nature that tend to produce slight variations 

 in results, these temperatures are referred to as being approxi- 

 mate. It is probable that future experiments may cause slight 

 changes to be made in these conclusions. Nothing more than a com- 

 paratively slight variation is to be expected, however. In practice 

 the beekeeper, in destroying these germs by heating, will naturally 

 use a quantity of heat somewhat in excess of the minimum amount 

 that is absolutely necessary. 



Some generalizations may now be made which will be of interest to 

 the beekeeper. The melting point of beeswax is between 62° C. 

 (143.6° F.) and 64° C. (147.2° F.), inclusive. It will be observed that 

 this same temperature in 10 minutes will destroy the germ causing 

 European foul brood, and that it is about 10° F. above that which will 

 destroy the germs of sacbrood and Nosema disease. A further inter- 

 esting generalization may be made concerning the heating of honey. 

 Honey when heated to 160° F. reaches a temperature 15° F. above the 

 temperature necessary to destroy the germ of European foul brood 

 and about 25° F. above the temperature that will destroy the infect- 

 ing agents of sacbrood and Nosema disease. The infecting agents of 

 these three diseases of the bee, therefore, will be destroyed when the 

 temperature of 160° F. is used in the commercial handling of honey. 

 Finally, it is believed that the results of this work on the thermal 

 death point of the viruses of the bee diseases will be directly applica- 

 ble to the control of these diseases. 



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