s 



EXPERIMENT STATION BULLETIN 



with as many as six applications had low ratings. None of the six or- 

 chards with an average of nine applications had ratings over 90 although 

 none was under 70. 



NUMBER OF ORCHARDS 



14 

 12 

 10 



8 



6 



^ 



8 

 PER CENT OF ORCHARDS 

 100 

 80 

 60 

 40 

 20 



20 

 40 

 60 



80 



1 



LESS THAN 5 



T 



■i 



CONTROL 



VERY GOOD 

 GOOD 



UNSATISFACTORY 



6 OR OVER 



NUMBER OF SPRAYS 



Figure 5. — Control ratings of orchards applying varying number 



of sprays per season 



However, when the farms were divided into three groups accord- 

 ing to the average number of sprays applied, six out of seven orchards 

 with less than five applications had unsatisfactory commercial control, 

 five out of 16 orchards with an average of five sprays, three out of 17 

 with six or more applications had unsatisfatcory commercial control. 

 (Figure 5.) These data show a tendency for the group of orchards with 

 fewer number of spray covers to have higher proportions of orchards 

 with unsatisfatory commercial control. It is significant that 83 per cent 

 of the operators in the group applying a small number of applications 

 had unsatisfactory control as compared to 25 per cent and 18 per cent 

 in the groups making more numerous applications. On the other hand, 

 the data indicate that high control depends on additional factors. The 

 data in Figure 5 indicate a considerable dispersion in control with the 

 same number of sprays 3 . From observations in the field it is thought 

 that the orchardists who apply a large number of sprays and yet do not 

 get good results are not careful in getting spray material to the top of 

 the trees and in covering other parts thoroughly. 



Gallons of spray applied and control 



The amount of spray applied per mature-tree equivalent varied from 

 8 to 61 gallons. Eleven of the 40 farmers applied less than 20 gallons, 



3 The coefficient of correlation between average number of sprays and control rating is: r = .39. 



