38 BULLETIN 809, U. S. DEPARTMENT OF AGRICULTURE. 



SACBROOD 



Sacbrood is recognized (25) by the death of larvae in capped cells 

 and not of pupae, by the saclike appearance of the dead remains, 

 and by the absence of viscidity. The absence of microorganisms 

 in the remains characterizes the microscopic picture. 



OTHER CONDITIONS 



Other brood conditions referred to as chilled brood, overheated 

 brood, starved brood, and in some cases drone brood, must be differ- 

 entiated from American foulbrood. The history of the case, the 

 age of the brood at the time of death, and the absence of ropiness 

 and of the foulbrood odor, usually make the diagnosis comparatively 

 easy. 



In some of the disorders of adult bees excrement of the adult bees 

 is sometimes found in the cells of the brood combs. When dry the 

 masses resemble somewhat brood-disease scales. The character of 

 the masses together with the microscopic picture is usually sufficient 

 for a diagnosis. In these cases a stained preparation is preferable. 

 The fecal matter contains bacterial rods in large numbers. In all 

 of these conditions the absence of B. larvae furnishes definite evidence 

 that American foulbrood is not present. 



PROGNOSIS 



Without treatment the prognosis in American foulbrood is deci- 

 dedly grave, the rule being that the colony sooner or later dies as a 

 result of the disease. This is true for experimental colonies and is 

 true also, as has been proved by the experiences of beekeepers, for 

 colonies in which the disease has occurred through natural means. 



A colony heavily inoculated experimentally is not destroyed by 

 disease in one month or two months. Loss in strength may be 

 apparent, however, after one month. If a colony is inoculated early 

 in the season and is heavily infected, it may die by midsummer; if 

 less heavily infected, it may live longer but die later in the season. 

 The infection may be so slight, indeed, that the colony may not be 

 destroyed directly but be so weakened that it will die during the 

 winter or surviving emerge a weakened colony in the spring and then 

 die of the disease during the following bee season. When a colony 

 during the summer contains much dead brood and becomes very 

 weak as a result of the disease, it usually absconds. The queen is 

 to be found among the bees to the last, and stores are not wanting 

 as a rule. 



A question of considerable interest but one which has not yet been 

 completely answered is: Does an American foulbrood colony ever 

 recover without treatment ? Some beekeepers have entertained the 



