SACBROOD. 



37 



RESISTANCE OF SACBROOD VIRUS TO DRYING AT ROOM TEMPERATURE. 



In the experiments made for the purpose of determining the amount 

 of drying which the virus of sacbrood will withstand, larvas recently 

 dead of the disease were used. These are crushed, strained through 

 cheesecloth, and the crushed mass poured into Petri dishes (fig. 32) to 

 the extent of a thin layer for each dish, the material in each being the 

 crushed remains of about 30 larvse. These are placed in a drawer, 

 shielding the larval material from the light. The drying then pro- 

 ceeds at the temperature of the room. This temperature varied 

 greatly from day to day, sometimes being as high as 93° F. (34° C). 



At intervals, reckoned in 

 days, after the preparation 

 of the virus, colonies are 

 inoculated. An aqueous 

 suspension is made of the 

 drying larva] content con- 

 tained in a Petri dish. 

 This is added to sirup, and 



the sirup suspension is fed to a healthy colony, 

 gave the following results : 



Fig. 32.— Open Petri dish. One-half of Petri dish, either 

 top or bottom. (Original.) 



The experiments 



Table IV. — Resistance of sacbrood virus to drying at room temperature. 



Date of inoculation. 



Time of drying. 



Results of inoculation. 



Aug. 8, 1914.. 

 Aug. 14, 1914. 

 Sept. 6, 1915. 

 July 1,1915.. 

 Sept. 28, 1915 

 July 6, 1915.. 

 Sept. 3, 1915. 

 Sept. 27, 1915 

 Oct. 9, 1914.. 

 July 29, 1915. 

 Sept. 3, 1915. 



Do 



May 22, 1915. 



Do 



3 days 



7 days 



13 days 



16 days 



18 days 



20 days 



22 days 



26 days 



28 days 



28 days 



35 days 



45 days 



7 months 12 days 

 7 months 21 days 



Sacbrood produced. 



Do. 



Do. 



Do. 



Do. 



Do. 

 No sacbrood produced. 



Do. 



No. 



Do. 



Do. 



Do. 



Do. 



Do. 



From the results recorded in Table IV it will be noted that the virus 

 of sacbrood in the experiment referred to withstood drying at room 

 temperature for approximately three weeks. 



The inoculations made during the third week indicated, by the re- 

 duced amount of sacbrood produced, that much of the virus had 

 already been destroyed. Obtaining negative results from the use of 

 larval material which had been drying more than seven months tends 

 toward eliminating the possibility that the virus possesses a resting 

 stage. 



