ANALYSIS OF PREHARVEST DROP CONTROL METHODS FOR 1959 



In 1959 It was suggested in our drop control reconmendations for Mcintosh 

 that a S].ngle spray of 10 ppm of NAA (naphthaleneacetic acid) plus 20 ppm of 

 2,4,5-TA (2,4,5-trichlorophenoxyacetic acid) might control preharvest drop about 

 as effectively as two separate sprays of 20 ppm of NAA applied about 10 days apart. 

 Did our 1959 results continue to support this contention? In Table 1 are our 

 1959 results. 



Table l.--The influence of chemicals on the preharvest drop and firmness of 

 Mcintosh apples. 1959. 



L. S. 



D. - 5% level 



5.2 



0.5 



7 trees per treatment. 



From the data shown in Table 1 it is apparent that treatment 2 (NAA applied 

 twice) resulted in less total drop by September 25 than any other treatment even 

 though the difference in control between it and treatment 4 (NAA plus 2,4,5-TA 

 combination) is not great enough to be statistically significant. These data and 

 those collected in 1958 show that the second application of NAA is slightly more 

 effective than 2,4,5-TA during the latter part of the drop period. For example, 

 from September 18 through 25, Treatment 2 had losses of 5.3 per cent; whereas, 

 trees in Treatments 3 and 4 had a 9.5 and 7.8 per cent loss of crop, respectively. 

 In other words, two NAA sprays (Treatment 2) gave 2.5 per cent better control than 

 Treatment 4 from September 18 through 25 and also 3.5 per cent from September 4 

 through 25. One may ask "Why worry about such small percentage differences in favor 

 of two sprays of NAA since a single combination spray of NAA plus 2,4,5-TA saves 

 the cost of one application?" In order to answer this question we need to know 

 how many boxes are involved per acre in a 2 to 5 per cent difference in control 

 and the cost of a hormone application. 



If preharvest drop hormones are applied by plane. Table 2 compares the cost 

 of two NAA sprays with a single NAA plus 2,4,5-TA spray. 



Table 2. --The approximate cost per acre of applying drop 

 control hormones by airplane (from information supplied 

 by D.H. Marsden, Eastern States Farmers' Exchange). 



Material 



Type 



2 sprays 

 NAA-20ppm 



1 spray 



NAA-lOppm plu 

 2,4,5-TA-20ppnl 



Cost/, 



acre 



$4.50 



$4.13 



Airplane 

 cost/acre 



$5.00 



$2.50 



Total 

 cost/acre 



$9.50 



$6.63 



