8 MASS. EXPERIMENT STATION BULLETIN 381 



to a large tree — then a spray should be applied immediately provided the 

 crop can and will be harvested within about 12 days. With some other 

 varieties a spray application may precede the harvest date by considerably 

 longer periods than is the case with Mcintosh. For instance, the effect 

 with Winesap has persisted longer than 4 weeks from the date of spraying. 

 However, with all varieties there is a time limit beyond which effectiveness 

 decreases markedly. With Mcintosh and Wealthy this interval seems to 

 be peculiarly short. 



Effect of a Single Late Application 



It is possible, of course, to apply hormone sprays at any time after drop- 

 ping has begun. Common sense, however, imposes certain limits. For 

 instance, since the effect from an application will not be manifest for from 

 2 to 4 days, there obviously would be little justification for spraying trees 

 which are to be picked within 4 or 5 days. Furthermore, as the proportion 

 of a crop which has dropped increases, the probability of an economical 

 use of hormone sprays decreases. Finally, a point is reached where an 

 application is not justified. 



It has been stated that a spray should go on very soon after dropping 

 has commenced in some volume. But suppose that a grower, for some 

 reason or other, fails to pick or to spray a block until one day he observes 

 that perhaps one-third of the crop is on the ground? Furthermore, he 

 figures that he will not be able to pick the block for another week. Will 

 hormone sprays be helpful? This question cannot be answered categorical- 

 ly because no two situations are strictly comparable. Table 3 illustrates 

 what happened in one such case in an experimental block at Massachusetts 

 State College. 



Table 3. — Average Cumulative Percent Drop of Original Crop. 

 (Sprayed September 28 — Harvested October 7) 



This test (Number 4) is separated into two parts: (a) young trees, 

 (b) mature trees. It is interesting to note the similarity of results. The 

 spray, which included one pint of oil per 100 gallons, was applied on Sep- 

 tember 28. The effect is barely discernible in the table on October 2 and 

 becomes progressively more pronounced up to the time of harvest. It 



