SPRAY MANAGEMENT 11 



Number of sprays and amount of calyx spray and control 



So far the number of sprays, the amount of total spray material, and 

 the amount of calyx spray have been related to control independently 

 and without regard to relationship. The combination of number of 

 sprays and the amount of material applied in the calyx application is 

 noted here' 1 . (Figure 8.) 



The orchards were divided into three groups. In group 1, con- 

 sisting of seven orchards with few applications and small amounts of 

 material at each application, 86 per cent of those orchards secured un- 

 satisfactory control. In group 2, consisting of 22 orchards with more 

 than five applications but with small amount of material each time, 36 

 per cent of the orchards obtained unsatisfactory control. All 1 1 farms 

 in group 3 were covered with more than five sprays and over 10 gal- 

 lons of spray material at each application and all had satisfactory control. 



The statistical data indicate that numerous heavy applications tend 

 to result in satisfactory control. Yet a few orchardists secure control with 

 five or six sprays and moderate applications each time, and a few others, 

 who apply the usual standard sprays and use moderate to heavy applica- 

 tions, do not get very good control. 



Skill and timeliness 



The data indicate that other factors in addition to number of sprays 

 and gallons of material are involved in control. Evidently, skill in ap- 

 plication and timeliness are important factors. The spray records, sup- 

 plemented by observations of the fieldmen, indicate that the skill of the 

 operator in applying the material so as to cover all parts of the tree and 

 the timeliness of the applications are important factors in successful con- 

 trol. The number of sprays and the gallons applied describe only part 

 of the operation. The material must be applied at the right time and the 

 entire foliage must be covered for satisfactory results. For instance, the 

 fieldman observed that several orchardists failed to cover the tops of the 

 trees. In other cases, unfavorable weather conditions limited the time 

 available for the application of a definite spray. Some of the operators, 

 through experience, are able to make an adequate cover even if the 

 weather is not ideal. One operator reported that a wind came up which 

 handicapped the spray operation but because of the limited time avail- 

 able he continued. In a few days, when conditions were favorable, part 

 of the orchard inadequately sprayed was covered again. In a few weeks 

 it was evident that the part of the orchard which had not been re-sprayed 

 had a great deal of scab. This is one example of need of a timely and 

 adequate cover, and shows the inadequacy of depending on the num- 

 ber of sprays or gallons of spray to obtain control. 



Skill in management and in application are highly essential 



It may be significant that some of the operators who secured very 

 good control did not have trees over 30 years of age. Control in young 

 vigorous orchards is more easily obtained. This is an important factor 

 in determining the commercial age limit of an orchard. 



6 Dr. G. N. Bauer, using the detailed data from the 40 farms, computed an equation of esti- 

 mate Xj = 43.0 _|_ 3.9 X _L 1.S5 X, _L 7.6. Where Xj — control ratings, X 2 — number of 

 sprays and X, == gallons of calyx spray per mature tree equivalent. 

 The coefficient of multiple correlation was found to be R,.,, — .65. 



