40 



BULLETIN 431, U. S. DEPARTMENT OP AGBICULTtTEE. 



RESISTANCE OF SACBROOD VIRUS TO DIRECT SUNLIGHT WHEN SUS- 



PENDED IN HONEY. 



The crushed and strained tissue mass of larvae dead of sacbrood 

 was susj)ended in honey and exposed to the direct rays of the sun. 

 To prevent robbing by bees, closed Petri dishes were used. At 

 intervals reckoned in hours healthy colonies were inoculated, each 

 with the virus from a single Petri dish. The exposures were made 

 during the day between 9 and 4 o'clock, preference being given to 

 the hours near midday. The group of experiments conducted on 

 this point gave the following results : 



Table VII. — Resistance of the sacbrood virus to direct sunlight when suspended in honey. 



Date of inoculation. 



Time of 



exposure 



to sun's 



rays. 



Besults of inoculation. 



Aug. 24, 1915. 



Do 



Aug. 18, 1915. 

 Sept. 9, 1915.. 

 Sept. 10, 1915. 

 Aug. 24, 1915. 

 Aug. 16,1915. 

 Aug. 25, 1915. 

 Sept. 8, 1915.. 



Do 



Sept. 9, 1915.. 



Do 



Aug. 25, 1915. 

 Sept. 11, 1915. 

 Aug. 26, 1915. 

 Sept. 11, 1915, 



Hours. 



1 



2 



4 



4 



4 



5 



5 



5 



5 



6 



7 



8 



10 



12 



13 



18 



Sacbrood produced. 



Do. 



Do. 



Do. 



Do. 



Do. 

 No disease produced. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



From the results of the experiments recorded m Table VII it wUl 

 be observed that the virus of sacbrood when suspended in honey 

 was destroyed by the direct rays of the sun in from five to six hours. 

 These figures represent the time for destruction of all of the virus 

 used in each experiment. The results obtained from the experi- 

 ments indicate, however, that much of it was destroyed earlier. 



LENGTH OF TIME THAT SACBROOD VIRUS REMAINS VIRULENT IN 



HONEY. 



In devising methods for the treatment of sacbrood it is of particular 

 interest to know the length of time that the virus will remain vindent 

 when it is ia honey. Experiments have been made to gain data on 

 this point. Larvae recently dead of sacbrood are crushed, strained, 

 and suspended ia honey. About one-half piat of the suspension, 

 representing the virus from about 30 dead larvae, is placed in each of 

 a number of glass flasks. These are allowed to stand at room temper- 

 ature, being shielded from the light by being placed in a closed cabinet. 



