Recent Studies on Peach Yellows and Little Peach 25 



son's growth, but these fruits fall from the trees in June even 

 though apparently perfectly pollinated and free from serious insect 

 or disease attacks. The rapid vegetative growth of the young trees 

 makes such a demand upon the carbohydrates elaborated in the leaves 

 that little or none is available for the fruit and the latter falls from 

 the tree from "starvation." Where the growth is not so rapid, an 

 occasional fruit may continue to develop, especially on some small 

 branch which is not making a very active growth. The senior author 

 has observed peaches mature and ripen on nursery trees the second 

 summer after budding, but these trees were on dwarf roots and did 

 not expend their all energy in vegetative growth. Trees only one or 

 two years of age from the bud occasionally produce fruit if their 

 growth is checked. 



Effect of Defoliation 



When a peach tree is partly defoliated by a caustic fungicide ap- 

 plied as a summer spray, the size of the fruit is below normal and the 

 tree growth may be slow or even completely checked. The loss of 

 foliage in such a case means a marked reduction in the amount of 

 carbohydrates elaborated, and even though the quantity used in sup- 

 porting vegetative development is small, the fruit also receives but a 

 small amount. This also applies to trees with scanty, weak foliage 

 resulting from other causes. 



Not only is the size of each individual fruit determined by the 

 amount of elaborated plant- food supplied to it, but its quality also is 

 modified. When peach trees are defoliated just before the fruit be- 

 comes ripe, the fruit may reach nearly normal size, but it is insipid 

 and lacks the sweetness of good fruit. In other words, the supply of 

 carbohydrates from the leaves has been cut off, the fruit ripens but is 

 lacking in this essential quality. This point also is well demonstrated 

 by cantaloupes when the foliage has been destroyed by blight. 



How Early in the Season Does Hate of Growth Affect Size of Fruit? 



Observations show that peaches of the same variety may vary 

 greatly in size on different trees soon after the fruit has set, where 

 there is a marked difference in the rate of growth of the trees. The 

 small green fruits on vigorous but slow-growing trees, where translo- 

 cation of foods is slightly checked, exceed in size those developing on 

 rapidly growing young trees. In other words, the fruit grower can 

 tell early in the season whether his trees are making the proper rate 



