BASIC COPPER SULFATE AS A FUNGICIDE 135 



4.00 per cent arsenic. The mixture applied on July 29 did not contain arsenic. 

 The amount of dust required increased with the growth of the plants but averaged 

 about 48.10 pounds an acre for each treatment. The persistence of the Colorado 

 potato beetle necessitated the continued use of arsenic. Two per cent nicotine 

 dust was appHed on July 27 and August 3 at the rate of about 20 pounds an acre 

 but did not prove particularly effective. Weather conditions and ladybugs, 

 however, prevented the rapid spread of aphis and leaf hoppers were not abundant 

 (A. I. Bourne). Foliage injury was inappreciable as a whole although occasionally 

 burning was observed where a large amount of dust accidently lodged on the plant 

 (J. P. Jones). For applying the dusts two hand dusters, the American Beauty 

 and the double action Cheeseman, were tested and gave "fair" distribution, but 

 the former was considered easier to operate and was employed. 



(!rowth was excellent until July 19, when yellowing of the lower leaves was 

 observed, apparently due to age or to excessive shading by the dense growth of 

 vines, as there was no evidence of disease and leaf hoppers and aphis were not 

 particularly destructive. By August 6 most of the leaves were severely injured by 

 tip burn and on August 20 nearly all were dead (Jones). The amount of early 

 blight was negligible but some late blight appeared about the first of September 

 after most of the foliage was dead and caused 1 to 2 per cent of tuber rot (Doran). 

 The yield of the several plots is reported on the basis of 60 pounds to the bushel. 



Table 7. Yield of Potatoes on the Rotation Plots. (^Per Acre.) 



Grade 1: All disease free potatoes above 1.75 inches in diameter. 



Grade 2: All disease free potatoes above 1 inch in diameter, not included in Grade 1. 



Grade 3: All disease free potatoes 1 inch or under in diameter. 



The low yield has been ascribed to leaf hoppers and aphis (Jones) and to the 

 effect of previous crops (Snell). The fact that the yield was appreciably larger 

 and the amount of rot less on the plots which were better located as to elevation 

 and natural drainage (Snell) would seem to indicate that the abnormal precipita- 

 tion during August was a limiting factor. As there were no check plots the effec- 

 tiveness of the dust must be judged largely from observations of the foliage and 

 the amount of tuber rot. 



A spraying experiment was conducted on the farm of G. Fred Pehssier at Hadley 

 (8 acres) to determine the relative effectiveness of basic copper sulfate and Bor- 

 deaux in controlling early and late blights on potatoes. The seed was certified 

 Rural Russets, raised by K. C. Livermore of Honeoye Falls, New York, and dis- 

 infected with corrosive sublimate. Planting was begun on May 4. The entire 

 field received similar cultural and fertilizer treatment and was sprayed seven 

 times from June 27 to September 9 at the rate of 100 gallons an acre. To the 

 major portion of the field was applied a mixture of Bordeaux 4-4-50 and lead 

 arsenate 2-50 containing about 0.24 per cent copper and 0.09 per cent arsenic. 

 Chemical hydrated lime or finishing lime (Tiger Brand) was used in place of 

 quickhme, pound for pound, in preparing the Bordeaux. To an inner strip of one 

 acre wasappUed a mixture of basic sulfate (lot 5), lead arsenate and raw linseed oil 

 2-2-0.5 pt.-50 containing about 0.25 per cent copper and 0.09 per cent arsenic. 



