52 DISEASES OF ECONOMIC PLANTS 



pays for itself year by year even if there be no general 

 epidemic. 



A few quotations from various sources to illustrate the 

 benefits of spraying are appended. 



" The return per acre from unsprayed area (grapes) is 

 calculated at 316 baskets per acre, worth less than $10 per 

 acre, while from the sprayed areas the average yield was 

 1252 baskets per acre, worth $125.20 per acre, secured at a 

 cost of .$7.50 per acre." — Ohio Bulletin, 130, p. 46. 



In New York (Geneva) in one case spraying for pear 

 scab at a total cost of 55 cents per tree increased the aver- 

 age yield from 45 cents to $6.55 per tree, a net profit of 

 $6.10 per tree. 



From records concerning plum spraying it appears that 

 where the trees were sprayed, the average per tree of picked 

 fruit was increased 44 per cent, the marketable drops in- 

 creased 8 per cent, and the waste decreased 81 per cent. 

 The total yield of marketable fruit as recorded in pounds 

 was 45 per cent greater where the trees were sprayed than 

 where they were not sprayed. 



In experiments at Tryon, N.C., the average weight of 

 good grapes obtained from a vine in the unsprayed rows 

 was 1 pound 1.5 ounces, as compared with 4 pounds 5.8 

 ounces from those given 6 sprayings with normal Bordeaux 

 mixture, a difference of 4 pounds 4.3 ounces to the vine, 

 or over a ton to the acre. This gain of a ton or more of 

 grapes to the acre was due entirely to the 6 sprayings, at a 

 cost of $15.42. 



The following table shows the results obtained with 

 potatoes in the volunteer experiments in New York during 

 the past five years, 1904-1908 inclusive : — 



