100 



Cumulative drop (%) 



Sept 13 



Sept 22 



Octi 



Oct 10 



Oct 19 



Figure 3. Cumulative drop after September 14 from trees that were or were not spot picked 

 on September 14 and received Alar or no drop controlling-treatment. 



Growers may wish to delay the appHcation of NAA 

 until they make their first harvest. This delay will allow the 

 filling of CA storages with fruit that has the potential for 

 long-term storage. When application of NAA was delayed 

 until trees were spot picked (September 14), it took ap- 

 proximately 6 days for drop control to be effective (Figure 

 2). During this period, over 25% of the fruit on NAA- 

 treated trees dropped. Once drop control was established, 

 NAA retarded drop for a long period of time. The results 

 of this experiment confirm the results of a similar experi- 

 ment done in 1986. In that study NAA was applied on 

 September 13 when drop exceeded 10%. It required 9 days 

 for NAA to slow drop significantly, and by that time over 

 20% of the crop had been lost. 



Spot picking removed about 39% of the crop. Even 

 though these trees were relatively small and are not difficult 



to pick, 6% dropped as the result of harvesting process. It 

 has been suggested that partial crop removal may reduce 

 drop. It is reasoned that the more mature fruit that are 

 prone to drop will be removed by spot picking. Also, the 

 snowball effect of one dropping fruit hitting another will be 

 reduced. Harvest did not reduce the amount of drop from 

 untreated trees (Figure 3). However, if trees were previ- 

 ously treated with Alar, crop removal did retard drop. The 

 reason for this is not clear. 



Summary . If NAA was applied when the first sound 

 apples started to drop it retarded drop effectively for 7 to 

 10 days. If NAA application was delayed until trees were 

 spot picked and drop was proceeding, it took up to 6 days 

 to slow drop. Over 25% of the crop was lost before drop 

 control was established. 



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