1908.] PUBLIC DOCUMENT — No. 33. 131 



plants affected were small and weak, and had not made the 

 OTOwth of the others. 



One week later the field was sprayed for the last time, as 

 after this the plants became too large to be sprayed again. 

 During the month of August the plants were inspected from 

 time to time, but no late blight {Pliytoplttliora infestans, 

 (DBy) ) occurred. In the first Aveek in September, however, 

 a disease appeared which seemed to make headway on some parts 

 of the field, although of no general occurrence on potatoes. 

 This was Cladosporium fidvum, Cke. A period of wet weather 

 lasting about a week and a half occurred just after the Clado- 

 sporium was noticed, and under these favorable conditions the 

 disease spread rapidly in some sections of the field. 



No more observations were taken of the plots until Septem- 

 ber 16, when the field was again examined carefully, both with 

 reference to the diseases present, the general appearance of the 

 plots and the maturity of the plants. These results were the 

 last taken before the potatoes were dug, and are given below. 



Regarding the diseases present on the different plots treated 

 with the spraying mixtures, it was found that plot 1 sprajed 

 with Bordeaux and Paris green, showed the presence of both 

 Alternaria and Cladosporium, although these diseases were 

 found only in localized areas, and could not be considered as 

 especially destructive to the plants. The Bordeaux and Paris 

 green is productive of fairly good results, but does not prove 

 to be so efficacious as some of the mixtures used on the other 

 plots. 



Plot 2, treated with Bordeaux and " Disparene," presented 

 a better appearance than did plot 1, and showed very little 

 Cladosporium or Alternaria. This was due to the fact that the 

 mixture adhered to the leaves for a longer time, and was not so 

 easily washed off" as the Paris green-Bordeaux mixture. 



Plot 3 was sprayed with Bordeaux and sodium benzoate, 

 and the plants proved to be in exceptionally fine condition, 

 practically no Alternaria or Cladosporium being found even 

 on dead plants. This mixture, although not coloring the 

 leaves to any appreciable extent, seemed to adhere better than 

 any of the others, with the exception of that used on plot 4. 



Plot 4 was sprayed with soda Bordeaux and Paris green, 



