364 ^ Report of the Mycologist of the 



discovered that the disease was beginning to attack the sprayed 

 plants and it was feared that the mixture used in the third and 

 fourth sprayings had not been strong enough to prevent the 

 germination of the fungus spores; and in the meantime it had 

 been ascertained that the injury done by the second spraying 

 was due to the Bordeaux mixture having been improperly pre- 

 pared. So in the fifth, sixth and seventh sprayings we used 

 Bordeaux mixture of the l-to-8 formula. 



Further experiments are necessary to determine what strength 

 of Bordeaux mixture will be the most satisfactory. The weaker 

 the mixture the less will be the expense of sjiraying, but. of 

 course, it must be strong enough to kill the fungus spores. 

 Judging from the behavior of the two test rows in Plat IV, one 

 of which was sprayed with 1-to-ll Bordeaux and the other with 

 l-to-7 Bordeaux, it seems probable that Bordeaux of the 1-to-ll 

 formula will prevent the disease just as effectually as stronger 

 mixtures. This opinion is strengthened by the fact that the 

 grape downy mildew is readily controlled by 1-to-ll Bordeaux, 



The quantity of Bordeaux mixture which it is necessary to use 

 at each application depends ui)on the size of the plants, the 

 amount of rainfall and the frequency with which the plants are 

 sprayed. The quantity required for the first spraying is small as 

 compared with the quantity required when the plants are full 

 grown. If the plants are sprayed once a week and there is little 

 rain between the sprayings, the quantity required each time will 

 not be nearly as great as when the plants are sprayed at longer 

 intervals and heavy rains occur. 



In the experiment, the quantity of Bordeaux mixture used in 

 the several sprayings was as follows: 



First spraying 25 gallons per acre. 



Second spraying 41 gallons per acre. 



Third spraying 53 gallons per acre. 



Fourth spraying 74 gallons per acre. 



Fifth spraying 141 gallons per acre. 



Sixth spraying 71 gallons per acre. 



Seventh spraying 71 gallons per acre. 



Total of seven sprayings 476 gallons per acre. 



