SACBROOD. 



39 



would naturally take place during the exposure to the sun would 

 tend also to destroy the virus, but as the resistance to drying is better 

 given in weeks than days, this factor may be disregarded here. 



RESISTANCE OF SACBROOD VIRUS TO DIRECT SUNLIGHT WHEN SUS- 

 PENDED IN WATER. 



In the experiments made for the purpose of determining the resist- 

 ance of the virus of sacbrood to the direct rays of the sun when 

 suspended in water, Petri dishes were again used. About 1| ounces of 

 the aqueous suspension containing the crushed tissues of 30 larvae is 

 poured into the dish and exposed to the direct rays of the sun. After 

 intervals reckoned in hours the inoculations of healthy colonies are 

 made. The contents of a single Petri dish are added to about one- 

 half pint of sirup and the suspension fed to a healthy colony. The 

 following results were obtained from the experiments: 



Table VI. — Resistance of sacbrood virus to the direct rays of the sun when 



water. 



Date of inoculation. 



Time of 



exposure 



to sun's 



rays. 



Results of inoculation. 



Sept. 10, 1915 

 Aug. 20, 1915. 

 Sept. 14, 1915 

 Aug. 24, 1915. 

 Aug. 18,1915. 

 Sept. 9, 1915.. 

 Sept. 10, 1915 

 Aug. 24, 1915. 



Do 



Aug. 16, 1915. 

 Sept. 8, 1915.. 



Do 



Sept. 9,1915. 



Do 



Aug. 25, 1915. 

 Aug. 20, 1915. 

 July 13,1915. 

 Aug. 26, 1915. 



Hours. 



Sacbrood produced. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 

 No disease produced. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



From Table VI it will be seen that when suspended in water the 

 virus of sacbrood was killed in from four to six hours. 



The aqueous suspensions in the Petri dishes in these experiments 

 did not reach by several degrees the temperature 138° F. (59° C.) at 

 which the virus is destroyed readily by heating (p. 34). Naturally 

 experiments of the nature of those in this group will vary in all cases 

 with the intensity of the sun's rays to which the virus is exposed. 

 The exposures were made in these experiments between 9 and 4 

 o'clock, the sun's rays toward the middle of the day being most 

 often used. 



