18 



CIRCULAR 



U. S. DEPARTMENT OE AGRICULTURE 



quently much more intense. It can sometimes be detected as soon 

 as a decayed larva is removed from the comb, and can also be 

 detected in the dry scales. 



A reliable symptom of this disease is a reddish-brown color and 

 ropy consistency of decayed brood, particularly when accompanied 

 by a pronounced putrid odor. 



SACBROOD 



Sacbrood is caused by a filterable virus, an organism so small that 

 it will pass through a porcelain filter and cannot be seen under 

 the most powerful microscope. Infection in the case of sacbrood 

 takes place by way of the alimentary canal. Both worker and drone 

 brood rnav be affected. It has not been definitely determined 



Figure l: 



•nib heavilv infected with sacbrood. showing numerous dead larvae. 



whether or not queen larvae are killed. Pupae are killed occasionally 

 but adult bees are not affected. 



IMPORTANCE 



Sacbrood is a widely distributed disease, but it usually does not 

 cause serious losses. It is important, however, for beekeepers to 

 recognize sacbrood so that it will not be confused with the foulbrood 

 diseases. 



Sacbrood may appear at any time during the brood-rearing season, 

 but it is most common during the first half of the season, and prac- 

 tically always subsides after the main honey flow has started. In 

 ordinary case- the colonies are not noticeably weakened by sacbrood. 

 but in exceptional cases, when 50 percent or more of the brood is 

 affected, they mav be considerably weakened. 



