THE McINTOSH DROP 15 



idea prevails that the blushed type of Mcintosh does not drop as much as the 

 striped type. As yet adequate data are lacking to clear up this point. However, 

 Dickson (4) reported practically the same percentage drops from blushed and 

 striped types over a period of years. He concluded that nutritional factors rather 

 than mutation may account for many of the "so-called non-dropping 'sports' of 

 Mcintosh." It is possible that certain soil factors influence dropping and that 

 these same factors favor light color which in turn would bring striping to atten- 

 tion. In Pennsylvania, Clarke'' has found evidence of variable dropping in 

 different strains but light dropping was not necessarily limited to the blushed 

 type. Probably the blush or solid red color can be associated with the non-dropping 

 faculty, but evidently this is not necessarily the case. Investigations on this 

 problem are under way at Amherst and it is hoped that definite progress can be 

 made in this field. 



Influence of Weather Conditions 



Undoubtedly, daily weather conditions influence daily dropping of apples at 

 harvest. Wind plays an indirect or secondary role in shortening the time that 

 an apple can remain attached after the initiation of abscission processes. Further-, 

 more, wind if severe enough produces unnatural drop by causing separation 

 without regard to normal abscission. 



Dropping records have been correlated with the various factors of weather with 

 somewhat uncertain results. Thus it is difficult to evaluate weather conditions 

 even though the significance of their influence is recognized. Under Amherst 

 conditions there has appeared some association between dropping and tem- 

 perature. For instance, in 1937, dropping was severe following the 24th and 

 25th days of September when high maximum temperatures were prevalent. 

 It is also significant that during that particular period, the total wind movement 

 was small. The records yield additional evidence on this point but the effects 

 often may be masked by other factors. It has been mentioned previously that a 

 summer temperature mean too high for a variety often causes severe early drop- 

 ing. This is evidenced with Mcintosh in the more southern sections of its range. 

 Blake* suggested that a drop following a period of high temperature may be due to 

 rapid carbohydrate respiration, especially on actively vegetative trees. Some- 

 times dropping has been more severe following a wet than a dry season. If the 

 carbohydrate-nitrogen ratio is a significant factor, as intimated previously, there 

 should be an association here. Hoffman (11) suggests that with equivalent ni- 

 trates available for growth, carbohydrate accumulation is less in a wet year. 

 Undoubtedly, then, the actual internal condition or perhaps growth status of a 

 tree in relation to its environment becomes an important focal point in the con- 

 sideration of the droping phenomenon just prior to and during the harvest 

 period. State of fruit maturity at any particular time is the net result of the tree- 

 environment relationship and hence is associated closely with drop. Since the 

 factors of weather are largely beyond our control the value of ascertaining their 

 separate and combined eff'ects on fruit drop lies in subsequently adapting cultural 

 practices to better fit the natural scheme of things. 



''W. S. Clarke, Jr. Corespondence. 1938 and 1939. 

 ''M. a. Blake. Correspondence, 1936. 



