UNITED STATES DEPARTMENT OF AGRICULTURE 



BULLETIN No. 780 



Contribution from the Bureau of Entomology 

 L. O. HOWARD, Chief 



Washington, D. C. 



PROFESSIONAL PAPER 



June 12, 1919 



NOSEMA-DISEASE. 



ByG. F. White, 

 Specialist in Insect Diseases. 



CONTENTS. 



Page. 



Introduction 1 



Name of disease .'... 3 



Digestive tract of adult bees 4 



Cause of Nosema-dlsease 7 



A tliree-year study of Nosema infection In an 



■ •. apiary. 13 



■ ' Symptoms of Nosoma-disease , 21 



-'Methods employed in experimental studies.. 22 

 ' ' Effect of Nosema infection on tlie colony and 



on the apiary 23 



'/'. '^ Resistance of Nosema apis to heating 29 



Resistance of ifoi«7no opis 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- 



intected colonies 43 



Resistance of Nosema apis to carbohc acid. . . 44 



Effect of drugs on Nosema-dlsease 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 aa infectious disease of adult honeybees. It 

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

 the colonies infected. »/Many colonies die qf 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 



