New York Agricultural Experiment Station. 303 



lack of flavor. Grapes affected by this insect show a decrease in 

 sugar and an increase in acid — two important factors in deter- 

 mining the quality of the product. In order to have exact data 

 showing the effects of injuries to the vines by this pest upon the 

 quality of the fruit, chemical analyses* were made of grapes 

 taken from sprayed and unsprayed vines, which are given 

 in Table I. For the reasons given below, comparisons of the 

 analyses can only be made as indicated — sample 3 with sample 

 5, 4: with 6, etc. 



It should be noted in these analyses: (1) That every sample 

 of Concord from ia sprayed section gave a gain in sugar over its 

 mate from the adjoining unsprayed section. These increases 

 varied from 8.4 per ct. to 68.1 per ct., an average of 27.0 per ct. 

 The two samples of Clinton grapes varied only 2.8 per ct. 



(2) That in every sample of unsprayed grapes except one 

 (Samples 7 and 8 which gave the same amount), the amount of 

 acid was greater than in the corresponding sample from a sprayed 

 vine. The excess of acid in the unsprayed grapes as compared with 

 those sprayed varied from per ct. to 20.6 per ct., an average of 

 11.2 per ct. 



(3) Grapes from the upper portion of a vine gave a higher 

 percentage of sugar than grapes from the lower portion of the 

 same vine ; on one vine the upper clusters showed 16.3 per ct. more 



* These analyses were made by Mr. 0. B. Winter, through the courtesy of 

 Dr. L. L. Van Slyke of the Department of Chemistry of this Station. The 

 taking of the samples received most careful attention, for unless care is exer- 

 cised in the selection of the fruit the data secured are worthless. For example, 

 analyses of two samples, one from upper portion and the other from the lower 

 portion of the same vine (Samples Nos. 20 and 21) show a difference of 

 sugar content, the grapes from the upper portion having 16.3 per ct. more 

 sugar than the grapes from the lower portion. Samples Nos. 22 and 23 from: 

 another vine on clay soil but poorly ripened show a difference of 9.7 per ct. 

 in sugar. In taking samples, two vines were selected that represented thel 

 average of the plat at that place, from the same soil, of the same age and 

 variety, the one sprayed, the other unsprayed ; an eight-pound basket of fruit 

 was picked from each, care being taken to select the fruit uniformly from all 

 portions of the vine; and duplicate samples were usually obtained from 

 another portion of the same vineyard. With all these precautions small 

 errors will undoubtedly occur in judging what constitute average vines, but the 

 selection of a number of samples, all of which give similar results, should be 

 fairly conclusive evidence that the data are reasonably accurate. 



