UNITED STATES DEPARTMENT OF AGRICULTURE 



1 BULLETIN No. 780 i 



J^9^^3L 



Contribution from tlie Bureau of Entomology 

 L. O. HOWARD, Chief 



Washington, D. C. 



PROFESSIONAL PAPER 



June 12, 1919 



NOSEMA-DISEASE. 



By G. F. White, 

 Specialist in Insect Diseases. 



CONTENTS. 



Page. 



Introduction 1 



Name of disease 3 



Digestive tract of adult bees 4 



Cause of Nosema-disease 7 



A ttiree-year study of Nosema infection in an 



apiary 13 



Symptoms of Nosema-disease 21 



Methods employed in experimental studies. . 22 

 EfEect of Nosema infection on the colony and 



on the apiary. 23 



Resistance of Nosema apis to heating 29 



Resistance of Nosema apis to drying 31 



Resistance of Nosema apis to fermentation. . . 33 



Page. 



Resistance of Nosema apis to putrefaction ... 35 



Resistance of Nosema apis to direct sunlight . . 37 



Period Nosema apis remains virulent 39 



Infectiousness of brood-combs from Nosema- 



infected colonies 43 



Resistance of Nosema apis to carbolic acid. . . 44 



Effect of drugs on Nosema-disease 44 



Modes of transmission of Nosema-disease 46 



Diagnosis of Nosema-disease 48 



Prognosis in Nosema-disease. 53 



Summary and conclusions 56 



Literature cited 58 



INTRODUCTION. 



Nosema-disease is an infectious disease of adult honeybees. It 

 causes the death of many individual bees, tending thereby to weaken 

 the colonies infected. Many colonies die of the disease, but the per- 

 centage of deaths is comparatively small and entire apiaries are 

 rarely, if ever, destroyed by it. It is not to be considered, therefore, 

 as a particularly serious disorder. This is shown by the results 

 recorded throughout the present paper. It is to be thought of rather 

 as a disease the losses from which are less to the infected apiary than 

 the losses from either of the foulbroods, although greater than those 



103789°— 19— Bull. 780 1 



