April, -IS] 



HUNGERFORD: TWO-SPR.\Y CALENDAR 



169 



infestation based on all apples set would seem to indicate that some 

 varieties do have a greater tendency to drop as a result of codling 

 injury than others. This may be used to determine the relation of 

 other insects to crop production, for while the per cent of codling 

 moth infestation of all apples set runs higher than the one based on 

 the apples picked, the reverse is true of cureulio. 



In the April Journal Doctor Ball states ''that records founded 

 upon picked fruit only are untrustworthy and practically valueless 

 for scientific purposes" and "that in all tests of efficiency absolutely 

 accurate accounts should be kept of every fruit that sets^ on the tree." 



By placing the two percentage columns together as they are in 

 €hart 3 we see that there is considerable difference in the individual 

 percentages and it is obvious that the one on the right more nearly 

 presents the efficiency of our spraying operations. 



COMPARISON OF CURCULIO INFESTATION OF SPRAYED AND UNSPRAYED ORCHARDS 

 Chart No. 4: 81,457 Apples Counted 



Comparing the sprayed and unsprayed trees with reference to cur- 

 eulio infestation (Chart No. 4 ) we see that in the unsprayed orchard 

 the infestation of the picked apples ranged from 17 per cent in the case 

 of the Black Twig to 48.5 per cent in the Winesaps, while in the block 

 sprayed twice the Black Twig showed an infestation of but 2.83 per 



1 In connection with the determination of efficiency in spraying operations it 

 might be of interest to note that Dr. S. A. Forbes as early as 1885 based the results 

 of his spraying experiments upon a history of all the fruit set. Dr. Forbes is, the 

 writer believes, the first to apply this method to insecticide work. 



