4 CIRCULAR 6 5 9, U. S. DEPARTMENT OF AGRICULTURE 



Under some conditions apples may start to drop before they are 

 properly mature. In such cases, of course, they are harvested al- 

 though they may not be sufficiently mature to develop the best quality 

 after ripening. Recently there has been an increase in the use of the 

 so-called hormone sprays, such as naphthalene acetic acid, to prevent 

 fruit drop (4). Use of a preharvest hormone spray invalidates the 

 ease of separation from the spur as a criterion of maturity. As a 

 result of this treatment the fruit can be retained on the tree longer 

 to become more mature and riper before harvest than if such sprays 

 are not used. 



GROUND COLOR 



The blush or red color of an apple is not a reliable index of maturity, 

 but with many varieties the ground color is. The quality of a red 

 apple can ordinarily be judged by the proportion of red to green; 

 the more red, the better the eating quality. But the ground color is 

 important in determining maturity, or when the apple should be 

 picked. As most varieties of apples become mature, the ground 

 color changes from a green very much like that of the leaves to a 

 lighter shade and eventually to yellowish. With most varieties the 

 time to pick is when the first signs of yellowing begin to appear, and 

 ordinarily there is no difficulty in determining when this time comes. 

 However, this is not always true with some varieties (Grimes Golden, 

 Jonathan, and Yellow Newtown as grown under certain conditions), 

 particularly with the various red bud sports that have been developed 

 in recent years. The latter usually become fully red before they are 

 mature, with no uncovered ground color left for observation. The 

 result has been that they have often been picked too soon and have 

 suffered in popular esteem because they are judged to have poorer 

 quality than the parent variety. Ground color cannot therefore ordi- 

 narily be used as an index of maturity in the red bud sports. How- 

 ever, it has been found that the red bud sports do not differ materially 

 in their season from the varieties from which they have been selected, 

 and it is therefore practicable to use the ground color of the parent 

 varieties for determining when to pick apples of the sports. 



PERIOD FROM BLOSSOMING TO MATURITY 



The problem of determining proper maturity has been of the most 

 concern to growers of the various red bud sports of the Delicious, par- 

 ticularly in the Pacific Northwest, where many plantings of the origi- 

 nal Delicious variety have been entirely replaced by Starking, Rich- 

 ared. or other red bud sports. When the difficulty in determining ma- 

 turity of these all-red varieties by customary indexes became apparent, 

 the United States Department of Agriculture began an investigation 

 to determine whether the length of time that must elapse from time of 

 blossoming to optimum maturity for harvest might be used as sug- 

 gested by Magness and others (10). The investigation has now been 

 in progress for several years. The results have shown that for satis- 

 factory eating and good storage quality at least 145 days must elapse 

 from the time of the first petal fall until the time of beginning harvest. 

 Limited observations in the section about Washington, D. C., have 

 indicated the same thing. Therefore, if growers in these sections will 

 observe the date when petals begin to fall from the earliest blossoms, 



