7 



(b) Cause of American Foulbrood 



In 1902 Dr. G. F. White, United States Department of Agriculture, 

 iirst demonstrated that the disease was caused by a bacteria which he 

 named Bacillus larvae. Certain bacteria have the ability to form a 

 protective covering around themselves. In this stage, called spores, they 

 are capable of existing for long periods away from their host. Bacillus 

 larvae is a spore forming bacteria. It will live for years in honey and 

 will often withstand boiling in water for twenty minutes. This spore 

 forming characteristic makes B. larvae very difficult to exterminate. 



(c) Method of Infection 



When honey is stored in cells containing scale the spores of American 

 Foulbrood become dispersed through the honey. Larvae fed with this 

 diseased honey become infected and death occurs a few days later. Thus 

 the cycle is maintained. 



(d) Methods of Spread 



American Foulbrood is spread chiefly by robbing infected honey from 

 diseased colonies, either dead or alive. Great care should be taken to see 

 that dead or weak colonies are not robbed out in the spring. The 

 entrances of these colonies should be closed or the hives removed to a bee- 

 tight dwelling about the first of April. This precaution is extremely 

 important. It is possible for one diseased colony to infect a whole apiary. 

 Infection may also be carried from one hive to another by drifting of the 

 nurse bees, especially during manipulation of the colony. Great care 

 should be taken in interchanging combs from one hive to another. Stray 

 swarms should be hived on foundation rather than on drawn comb. Then 

 if diseased honey is present in the crops of the swarming bees it is used 

 up in drawing out the foundation, rather than being stored and later fed 

 to the larvae. 



Bee trees are often given too much credit for the spread of disease. 

 Although colonies in trees may spread American Foulbrood, such swarms 

 which become weakened and die from disease do not long remain a 

 menace. They are soon cleaned up by wax moths, ants and other insects 

 or animals. 



(e) Immunity to American Foulbrood 



Although workers are most commonly infected, drones and queens 

 are also susceptible to the disease. From the results of experimental 

 inoculations and beekeepers' experience it appears that no race of bees 

 possess any marked immunity to the disease. 



(f ) Eradication of American Foulbrood 



The old shaking treatment, whereby the bees of a diseased colony are 

 shaken on to foundation and thus saved can no longer be advocated. In 

 fact, it has been found that the treatment in general tends to spread 

 disease rather than eradicate it. When combs are shaken there is a 

 tendency for young nurse bees, not having marked their location, to _ fly 

 into nearby hives carrying diseased honey with them. Another criticism 

 of the treating system aside from general spread of disease at the time of 

 treatment is that diseased combs are often stored for some time before 



