April, '08] JOURNAL OP ECONOMIC ENTOMOLOGY 137 



total fruit wormy by the first brood, with 10% benefit due to less 

 injury by worms entering the side of the apple, and the balance of 8% 

 due to benefit by fewer worms entering the calyx. 



One plot was given the fifth spraying (that is three weeks after the 

 petals dropped, or as the eggs were hatching) in the ordinary manner, 

 in this the apples being sprayed as well as the foliage, but not having 

 been previously sprayed, no poison was deposited in the calyx. This 

 plot gave a benefit of 25%, based on the percentage of the total fruit 

 wormy by the first brood, with a benefit of 15.7% due to fewer worms 

 entering the calyx, and 9% due to fewer worms entering the side. If 

 the benefit derived from spraying the foliage only upon the tree, 

 which was bagged, be subtracted from that secured on the plot where 

 both the foliage and apples were sprayed with the fifth spraying, we 

 get the benefit due to the spray on the apples as regards the first 

 brood, and find that it is about one-fourth of the value of this fifth 

 spraying, and consists entirely of a benefit due to fewer worms enter- 

 ing the calyx or about 7%. If we divide the value of the fifth spray 

 between the benefit derived from fewer worms entering the calyx and 

 fewer worms entering the side, according to these proportions, we find 

 that 9% out of the 25% is due to fewer worms entering the calyx and 

 15.7% due to fewer worms entering the side, or about two-fifths of 

 the benefit is due to the calyx and three-fifths to the side. 



But only 29% of wormy fruit are due to the work of the first brood 

 on the unsprayed trees. When the benefit done by the control of the 

 first brood alone is measured in terms of percentage of the benefit for 

 the whole season, we find that only 27.5% out of 96% is due to the 

 direct benefit on the first brood, where sprays III, IV and V were 

 given. As a matter of fact the benefit of these sprayings thru their 

 effect on the first brood is much greater than this and can only be 

 shown after we have considered their effect on the second brood. 



The addition of spray V did not seem to materially increase the 

 benefit to the first brood when given after spray III, but the addition 

 of spray IV and V to III show a very slight benefit over III and V. 



In order to determine the true benefit of the effect of sprays on the 

 first brood, we must find their effect on the second brood and by sub- 

 tracting it from the total effect for the season we secure the real 

 benefit due to the influence on the first brood, for it is evident that 

 by reducing the numbers of the fir.st brood there will be fewer of the 

 second brood, and the apparent total benefit to the second brood is 

 therefore really due to the effect of the lessened numbers due to the 

 killing of the first brood, as well as to the direct effect of the spray 

 upon the second brood. 



