PREHARVEST mOP CONTROL FOR 1960 



Our printed suggestions for preharvest drop control of apples (Special 

 Circular No. 254) will be identical with those of 1959. In the November - 

 December, 1959 issue of FRUIT NOTES, the pros and cons of two separate sprays 

 of NAA (10 days apart) are compared to one combination spray of NAA and 2,4,5-TA. 



As you may recall we are inclined to favor two sprays of double strength 

 (20 ppm) NAA in order to control Mcintosh drop for 3 weeks. Invariably two 

 such NAA treatments result in at least 2 or 3 per cent better drop control than 

 the NAA plus 2,4,5-TA single spray combination. As shown in Table 1, the dif- 

 ference in estimated per acre costs of these two methods of obtaining drop 

 control amounts to only $2.87 in favor of the single spray combination. How- 

 ever, if the NAA plus 2,4,5-TA combination is 2 or 3 per cent less effective 

 than two NAA sprays in drop control, the use of the combination represents a 

 loss of 10 to 15 boxes of fruit in a block producing 500 boxes per acre or a 

 20 to 30 box loss in a block yielding 1000 boxes per acre. When apples are 

 worth $2.00 a box, only 1.5 boxes of apples per acre need to be saved by the 

 double NAA spray to pay the extra cost of a second spray. Consequently, if 

 two NAA sprays are consistently a per cent or more superior to the single spray 

 (NAA plus 2,4,5-TA combination), two sprays of NAA represent a more economical 

 proposition. We are assuming that airplane service is available on a 24 to 48- 

 hour notice. 



It should be remembered that every now and then delaying the second NAA 

 spray for a full 10 days may coincide with a very warm period and a sharp in- 

 crease in fruit loss may occur for a couple of days before the second appli- 

 cation becomes effective. In such a situation the one spray combination may 

 be as effective as the two NAA sprays over the full three week period for Mcintosh. 



Table 1. The Approximate Cost per Acre of Applying Drop Control Hormones by 

 Airplane (from information supplied by D.H. Marsden, EgStern States 



Farmers' Exchange) 



•-F.W. Southwick 



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