2 FAHMEBS' BULLETIN 1713 



In performing such tasks as feeding the larvae, building the cells, 

 ripening the nectar, and transferring it from one part of the hive to 

 another, the bees may contaminate not only honey that is in the 

 brood nest, but also that in the supers above the queen excluder. 

 This does not mean, however, that all the honey in the brood nest 

 or supers necessarily becomes contaminated. 



Spores may come in contact with larvae of any age, but the larvae 

 rarely die until they have developed to the point where they lie 

 lengthwise in the cells or the cells are being sealed preparatory to 

 transformation to pupae. During the early coiled stages the sugar 

 content of the larva is usually high and, since the germ of American 

 foulbrood will not grow in highly concentrated sugar or honey, it 

 is only after much of the body sugar has been utilized that the spores 

 can develop. Underfed larvae have a low sugar content, and in 

 contact with such larvae the spores are able to germinate and to kill 

 the larvae while they are still coiled. 



The spores of American foulbrood are invisible to the naked eye, 

 and they are extremely resistant to sunlight, drying, heat, and 

 commonly used chemical disinfectants. The maximum time that the 

 spores retain their virulence has not been determined, but they are 

 faiown to remain alive for years in honey and brood combs. 



SPREAD OF THE DISEASE 



It has always been considered that the disease is spread from 

 colony to colony most commonly by the robbing of hives containing 

 disease-weakened colonies or bees that have died of American foul- 

 brood, by bees from healthy colonies. Robbing* unquestionably 

 scatters American foulbrood. A disease-weakened colony does not 

 defend itself well; therefore it is possible for robber bees from 

 healthy colonies to help themselves to contaminated honey. On the 

 other hand, the beekeeper himself often unwittingly spreads the 

 disease within an apiary when he moves combs of brood and honey 

 from one hive to another, or unites weak colonies, which may be 

 diseased, with strong, healthy ones. These are probably the most 

 common means of spread. The disease may also be carried from one 

 colony to another when bees enter the wrong hive, a practice gen- 

 erally referred to as drifting. 



The dissemination of the disease beyond the range of flight of the 

 bee can be accounted for by the transportation of infected material, 

 including honey, into a disease-free area, where it is later made 

 accessible to healthy bees. Experimental evidence indicates that the 

 commercial shipment of honey is not such an important means of 

 spread as many persons suppose. The sale of used, contaminated 

 equipment is, however, one of the principal avenues through which 

 this disease is spread from one locality to another. 



A beekeeper who does not know anything about American foul- 

 brood, or how to check its spread in his apiary, will not be able to 

 maintain his colonies with profit if they become weakened by the 

 disease. Finding this to be the case, he may sell his empty hives, 

 combs, and other accessories, perhaps to another beekeeper who 

 knows no more about the bee diseases than he does. Purchasers of 



