340 



AMERICAN BEE JOURNAL 



October 



cause of American foulbrood, natural- 

 ly this disease can occur only when 

 the germ is present and alive. The 

 task of preventing the disease by 

 keeping the living germ away from 

 the apiary is not an easy one, al- 

 though much can be done in this di- 

 rection. The length of time the germ 

 will live under various environments 

 is, therefore, of first importance. 



Some idea relative to this point may 

 be gained from experimental obser- 

 vations which have been made. Scales 

 containing the spores of American 

 foulbrood were collected in 1907 and 

 kept in the laboratory until Septem- 

 ber, 1916. Each succeeding year, dur- 

 ing this period of more than 9 years, 

 tests were made, using some of this 

 scale material, and in every instance 

 the spores were found to be alive. It 

 was found, also, that they were as 

 resistant to heat, and, by the inocu- 

 lation of the colonies, they were 

 found to be as virulent at the end of 

 this period as at any previous time. 

 It has not yet been determined how 

 long the spores will remain alive in 

 the dry scales, but it is quite probable 

 that they will live much longer than 

 9 years. 



When the spores from the scale 

 material were suspended in water and 

 heated to boiling (212 degrees F) they 

 were all killed in 11 minutes. A half 

 hour or more may be necessary when 

 they are in honey. By employing a 

 higher temperature the period of 

 heating may be diminished. 



A water suspension of the scales 

 was poured in a thin layer on glass 

 plates and allowed to dry. These 

 films were exposed to the direct rays 

 of the sun. The spores were found 

 to remain alive for from 28 to 41 

 hours. They remained alive from 4 

 to 6 weeks when they were suspended 

 in honey and exposed to the sun. 



The spores added to honey and kept 

 away from the direct sunlight were 

 found to be alive and ^ irulent after 

 one year. It is very likely they are 

 capable of remaining so, a very much 

 longer period, in such an environment. 



In the presence of fermentation the 

 spores were found to be alive and 



virulent at the end of 7 weeks, and it 

 is quite likely they would have re- 

 mained so a very much longer period. 



In a 5 per cent carbolic acid solu- 

 tion the spores of American foulbrood 

 remained alive for months; in a 1 : 

 KXX) mercuric chloride solution, for 

 days; and in a 10 per cent formalin 

 solution for hours. 



From these facts it will be observed 

 that the spores of American foul- 

 brood are able to live over long peri- 

 o'ds in nature and that the beekeeper 

 cannot wait until they die a natural 

 death, if he wishes to make sure that 

 they are dead, but must take active 

 measures to destroy thetn. For prac- 

 tical purposes chemical disinfectants 

 are not suitable. Heat would seem to 

 be the most practical agent. Burning 

 or scorching, of course, will kill the 

 spores and the boiling of water or 

 honey containing them will cause 

 their destruction. In practical api- 

 culture a somewhat longer period 

 should be adopted, in using chemical 

 disinfectants to kill the spores, or in 

 boiling to destroy them, than is indi- 

 cated as being necessary in the ex- 

 periments which have been cited here. 



Experimental Studies on American 

 Foulbrood 



It is quite natural that a large num- 

 ber of questions concerning the bee 

 diseases should arrive in the minds of 

 beekeepers whose apiaries are^ in- 

 fected or threatened with infection. 

 Many of these questions can be 

 answered by the results of studies 

 which have been made on these dis- 

 eases in the experimental apiary. 

 During these studies not only have 

 the causes of the bee diseases been 

 discovered, but observations of inter- 

 est have been noted, regarding the 

 symptoms, the diagnosis and the 

 spread of the diseases, and the effect 

 of them on the colony and on the 

 apiary. During the work no experi- 

 ments were undertaken directly on 

 the treatment of the diseases, but in 

 selecting problems for solution such 

 were chosen as would yield informa- 

 tion which could be used by the bee- 

 keeper in devising new methods of 



Hive fur experimental colony. 



treatment or in improving those now 

 in use. 



A knowledge of the methods which 

 were devised and used, in carrying on 

 the bee disease study, is valuable not 

 only to the investigator who wishes 

 to pursue such studies, but also to the 

 practical beekeeper who, by becoming 

 familiar with the experimental pro- 

 cedure and the observations noted, 

 will be able to draw conclusions for 

 himself and to verify or disprove 

 those drawn by others. 



The American foulbrood studies 

 were conducted in the same apiary 

 (.Fig. 6) as were those on the other 

 diseases, and the methods used are 

 quite similar to those briefly dis- 

 cussed for Nosema-disease and Eu- 

 ropean foulbroodt in earlier articles. 

 From 3 to 5 scales were used, as a 

 rule, in making inoculations. A sus- 

 pension is made of these by grinding 

 them in a spoonful of water and then 

 adding this aqueous suspension to 

 syrup. The syrup suspension, which 

 now contains, millions of American 

 foulbrood spores, is then fed to a col- 

 ony free from disease. The same 

 kind of experimental hive (Fig. 7) 

 is used as was employed in the 

 studies of the other diseases. The 

 method of inoculation, by which 

 some 'of the contaminated food is 

 placed directly in the cell with the 

 larvae, is less satisfactory in studies 

 on American foulbrood than on the 

 other brood diseases. , 



The first symptom of American 

 foulljrood to be observed, after feed- 

 ing a colony the germs, occurs during 

 the seventh day following the hour 

 in which the feeding is done. Since 

 llie larva; and pup;c dead of American 

 foulbrood contain millions of spores, 

 any fragment of the dead brood is ca- 

 pable of producing the disease if it 

 reaches feeding larvae and is eaten by 

 tliem. The piecemeal removal of the 

 brood (Fig. 5, L) and the slight gnaw- 

 ing of it by the bees tend, therefore, 

 to spread the disease within the col- 

 ony. 



In a few instances only, during the 

 experimental studies, did the disease 

 seem to spread from the inoculated 

 to the healthy colonies of the apiary. 



I'lg. b. — L.\ittnijieiUal apiary iii which Aiiiericaii foulbrood was studied. 



" American Bee .louriial, July, August and 

 SL'iiteinber, 1919. 



t .\nierican Bee Journal. July and August, 

 1920. 



