UNITED STATES DEPARTMENT OF AGRICULTURE 



BULLETIN No. 431 



Contribution from the Bureau of Entomology 

 L. O. HOWARD, Chief 



Washington, D. C. 



PROFESSIONAL PAPER 



February 9, 1917 



SACBROOD. 



By G. F. White, 

 Expert, Engaged in the Investigation of Bee Diseases. 



CONTENTS. 



Introduction l 



Historical account 2 



Name of the disease 4 



Appearance of healthy brood at the age at which 



it dies of sacbrood 6 



Symptoms of sacbrood r — 10 



Cause of sacbrood 24 



Weakening effect of sacbrood upon a colony. . . 30 

 Amount of virus required to produce the dis- 

 ease, and the rapidity of its increase 31 



Methods used in making experimental inocula- 

 tions 32 



Means for the destruction of the virus of sac- 

 brood 34 



Heating required to destroy sacbrood virus 



when suspended in water 34 



Heating required to destroy sacbrood virus 



when suspended in glycerine 35 



Heating required to destroy sacbrood virus 



when suspended in honey 36 



Resistance of sacbrood virus to drying at room 

 temperature ', 37 



Resistance of sacbrood virus to direct sunlight 



when dry 38 



Resistance of sacbrood virus to direct sunlight 



when suspended in water 39 



Resistance of sacbrood virus to direct sunlight 



when suspended in honey 40 



Length of time that sacbrood virus remains 



virulentin honey 40 



Resistance of sacbrood virus to the presence of 



fermentative processes 41 



Resistance of sacbrood virus to fermentation in 



diluted honey at outdoor temperature 42 



Resistance of sacbrood virus to the presence of 



putrefactive processes 43 



Resistance of sacbrood virus to carbolic acid. . . 44 



Modes of transmission of sacbrood 4G 



Diagnosis of sacbrood 48 



Prognosis 49 



Relation of these studies to the treatment of 



sacbrood 50 



Summary and conclusions 52 



Literature cited 53 



INTRODUCTION. 



Sacbrood is an infectious disease of the brood of bees. It is fre- 

 quently encountered and has often been the cause of fear on the part 

 of beekeepers through a suspicion that one of the more serious 

 maladies — the foulbroods — was present. 



The disease is more benign than malignant. It is insidious in its 

 nature and somewhat transient in its character. The number of 

 colonies that die as a direct result of sacbrood is comparatively small; 

 the loss of individual bees from it, however, in the aggregate is 

 enormous. The loss tends naturally to weaken the colony in which 

 the disease is present, a fact which makes the disease one of great 

 economic importance. 



58574°— Bull. 431—17 1 



