VOL. LX— NO. 7 



HAMILTON, ILL., JULY, 1920 



MONTHLY, $1.00 A YFAR 



Some Observations on European Foulbrood 



By G F. White, Bureau of Entomology, U. S. Dept. Agr., Washington, D. C. 



EUROPEAN foulbrood is an infec- 

 tious disease of honeybees that 

 is characterized by the death of 

 the brood during its uncapped stage, 

 and by the absence of both ropiness 

 and disagreeable odor. Studies on 

 the disease were made by the writer 

 from 1902 to 1916 and some of the ob- 

 servations are given in the present 

 article. Those who may be interested 

 in the results obtained can find a 

 more detailed summary of ithem in 

 Bulletin 810.* No work directly on the 

 treatment of the disease was at- 

 t mpted, but in choosing problems for 

 study those were selected which by 

 their solution would furnish informa- 

 tion tha't could be applied readily by 

 the beekeeper in any revision of 

 methods of treatment now in use, 

 which might be needed, or in devis- 

 ing new ones. 



Causes of European Foulbrood 



European foulbrood can be pro- 

 duced experimentally (Fig. 1.) by 

 feeding a colony syrup which con- 

 tains the crushed bodies of larvae 

 sick or dead of the disease. The lar- 

 vae become infected during the feed- 

 ing stage, infection taking place at 

 some time during the period from 

 about 2 days of age to capping. Lar- 

 vae live more than 2 days after be- 

 coming infected. If they die, there- 

 fore, they are 4 days old or older at 

 the time of death. Since larvae are 

 capped about 4 days before pupation, 

 it is to be expected tha't death would 

 occur before the pupal stage is 

 reached, and this is what happens. 

 Worker, drone and queen larva are 

 susceptible to infection ; adult bees 

 are not. This is true of all races of 

 bees kept by American beekeepers. 



Since European foulbrood occurs 



• Bulletin 810. European Foulbrood. U. S. 

 Department of Agriculture, Feb. 26, 1920. 

 The Bulletin was prepared primarily for the 

 beekeeper, but others also in studying the bee 

 diseases, may find it useful. Those who may 

 be interested, particularly in the more practi- 

 cal portions of the paper, can well omit the 

 parts of it which are technical. 



at least in Austria, Denmark, Eng- 

 land, Germany, Switzerland, Canada 

 and ithe United States, the disease 

 cannot be attributed entirely to cli- 

 matic conditions nor to the kind of 

 food obtained by the bees. The course 

 of the disease is affected somewhat, 

 however, by the quantity of food ob- 

 tained and by ithe season of the year. 

 The exciting cause of European 

 foulbrood is a germ f (Fig- 2) that is 

 taken into the stomach of the larva 

 with its food. The name of it is Ba- 

 cillus pluton. It is very small, about 

 25,000 of them placed end to end 

 measure an inch. Some are spherical, 

 others are egg-shaped, while most of 

 them in larvae that are dead of the 

 disease, or nearly so, are more or less ' 

 oval, and with somewhat pointed 

 ends. The germ does not bear spores. 

 Being the cause of European foul- 

 brood, it is always present in brood 

 sick or dead of the disease. 



■|- The "germ" causing European foulbrood is 

 a very small plant which, after reaching the 

 stomach of the larva, grows, multiplies and pro- 

 duces sickness and usually death of the larva. 

 It belongs to a group of plants called bac- 

 teria. "Microbe" and "parasite" are some- 

 times used instead of the term "germ." Ba- 

 cillus pUtton is a convenient name for this 

 plant. The other germs found in this disease 

 are plants also. 



Other germs are almost invariably 

 found in brood dead of European 

 foulbrood, but none of these addi- 

 tional ones cause disease. One of 

 them is Bacillus alvei (Fig. 3). This 

 is an elongated slender rod; about 

 10,000 are required to measure an 

 inch. It produces spores. By com- 

 paring Bacillus pluton (Fig. 2) and 

 Bacillus alvei (Fig. 3) one can readily 

 see that they are very different 

 germs. 



Another germ which does not pro- 

 duce disease, but which is occasionally 

 present in brood dead of European 

 foulbrood is Streptococcus apis (Fig- 

 4). This one is more or less spher- 

 ical and resembles Bacillus pluton 

 (Fig. 2) both in size and form. The 

 two, however, are very different, more 

 so, probably, 'than is the apple tree 

 different from the oak. 



Names of the Diseases 



The names that are at present being 

 used for the brood diseases in the 

 different countries are rather inti- 

 mately connected with studies made 

 on the germs contained in the brood 

 dead of the different diseases. In 

 1885, Bacillus alvei was found in brood 

 dead of foulbrood by Cheshire and 

 Cheyne of England, and for about a 



Fig. 1. European foulbrood produced experimentally 



