DIAGNOSING BEE DISEASES IN THE APIARY 6 



When dead brood is found, the following important points should 

 be determined: (1) Age of the brood when death occurred, (2) po- 

 sition of the dead brood in the cells, (3) color of the dead brood, 

 (4) consistency of the dead brood in different stages of decay, (5) 

 odor coming from the combs, and (6) odor of dead larvae in different 

 stages of decay. 



A guide for use in diagnosing diseases of the brood of bees is given 

 in table 1 (pp. 22-23). 



It should always be kept in mind that more than one brood dis- 

 ease may be present in a colony. Of -first importance at all times is 

 the early discovery of American foulbrood. When a less serious 

 brood disease is found, it should be determined whether or not Amer- 

 ican foulbrood also is present. 



American Foulbrood 

 cause 



American foulbrood is an infectious disease of the brood of bees 

 caused by a bacterium known as Bacillus larvae. It is the most de- 

 structive of the brood diseases, is very infectious, and most diseased 

 colonies eventually die. Although progress is being made in breed- 

 ing resistant strains of bees, as yet no breeder can guarantee 100 per- 

 cent of resistant queens. Similarly, while apparently excellent re- 

 sults have, in many cases, been obtained from feeding sulfa drugs to 

 colonies, it is too early to know whether the disease is actually cured, 

 or only "driven into hiding." 



The concentrations of sulfa drugs used in treating American foul- 

 brood do not kill B. larvae spores. Hence, live spores may remain 

 in the comb in apparently "cured" colonies, later to reinfect the 

 colony or, with interchange of equipment, to infect other colonies. 

 Many such occurrences have been reported. 



B. larvae causes the death of bee larvae and pupae by its growth 

 and multiplication within the stomach, and after the cells are sealed 

 causes a typical decay of the dead brood. The spores resist drying, 

 the action of chemicals, both high and low temperatures, and the de- 

 hydrating action of honey. Consequently American foulbrood can- 

 not be treated successfully by most beekeepers except by burning the 

 infected combs and bees. 



EFFECT UPON THE COLONY 



The strength of a recently infected colony will not be noticeably 

 affected, and there will be only one or a few dead larvae or pupae in 

 sealed cells with slightly discolored or sunken cappings. The dis- 

 ease may not develop to a critical stage and seriously weaken the 

 colony until the following year, or it may advance more rapidly and 

 seriously weaken or kill the colony the first season. If the disease 

 has been present and active for a considerable period, the colony will 

 be noticeably weakened, and a large proportion of the cells (75 per- 

 cent or more) will contain dead brood. All weak, infected colonies 

 found at any time of year should be burned at once to prevent spread 



