648 MICROBIAL DISEASES OF INSECTS 



climates where the breeding season is prolonged, the rapidity of devas- 

 tation is more marked. 



Causal Organism. — Bacillus larva, a motile, spore-producing bacillus is the 

 etiological factor in American foul brood. It is cultivated with difficulty, growing 

 best on media made as the ordinary laboratory media, substituting bee larvse for 

 meat. On these media it produces a large number of giant whips which persist for a 

 long time. These giant whips are also found in decaying larvae which are dead from 

 American foul brood experimentally produced by feeding pure cultures of B. larva. 

 B. larva and its spores are killed at 9o''-ioo° in ten minutes, and at 100° in less than 

 five minutes. 



Methods of Inpection.— Artificial. — ^American foul brood can be 

 communicated by feeding to a healthy colony the scales from combs 

 which had contained brood affected with American foul brood; likewise 

 when these scales are placed in ordinary meat broth, incubated twenty- 

 four hours and then heated to 65° for twenty minutes; infection in this 

 case is due to the presence of spores. Pure cultures of B. larva mixed 

 with sterile sugar sirup and fed to healthy colonies produces the disease 

 within three weeks. B. larva can be obtained in pure culture from 

 such diseased larvae. 



B. larva may be, obtained in large quantities suitable for experi- 

 mental inoculation by diluting and filtering the crushed bodies of 

 bee larvse through a Berkefeld or other fine filter. 



CoNTKOL. — ^The treatment of an infectious bee disease consists 

 primarily in the elimination or the removal of the cause of the disease. 

 Effort is not made to save the larvas already dead or dying, but to stop 

 further devastation by removing all material capable of transmitting 

 the cause of the trouble. The swarm is transferred from the infected 

 hive to a clean disinfected hive; the infected combs from the old hive 

 should either be burned, melted, or boiled thoroughly before the wax is 

 fit for use again. The honey taken from the infected hive should be 

 buried or at least removed so that no bees can use it for food. This 

 treatment may have to be repeated before the disease is under control. 

 Brood from badly diseased colonies should be burned, buried or other- 

 wise destroyed at once. Combs even if they appear white and clean 

 should be melted. Infected hives should be burned over inside with 

 a gasoline or oil torch. 



