Recent Studies on Peach Yellows and Little Peach 41 



nursery in August. Several trees were secured from each lot and 

 planted in a chicken yard after they were one year old. All those 

 propagated from the diseased branch became diseased within the first 

 two years after planting but the trees propagated from the appar- 

 ently healthy branch have remained healthy to date (1921). This 

 has been the only case of this sort found at the New Jersey station. It 

 is probable that there are instances where an entire tree may not be 

 affected with yellows or little peach after one branch has begun to 

 sbow unmistakable symptoms of the disease. It is not believed that 

 such a condition would continue for very long. 



Pollen not a Carrier of Disease 

 During the early spring of 1916, the junior author, in conducting 

 breeding work with peaches, planned some crosses in which a tree of 

 the variety Dewey located on the College Farm was used as a pollen 

 parent. Soon after the tree set fruit it developed unmistable symp- 

 toms of yellows and was pulled out and destroyed. In the meantime 

 the pollen had proved to be viable and a good set of fruit resulted 

 from the crosses. The pits secured from the crosses were stratified 

 and planted in the nursery row in the spring of 1917. A total of 45 

 trees were obtained and these were planted out in orchard form in 

 the spring of 1918. They are now (May. 1921 ) entering upon their 

 fourth season's growth in the orchard. Thus far they have shown no 



symptoms of disease. , ™ 



' F Starch Tests 



During the seasons of 1913 and 1914, the horticulturist found the 

 time available to make some special starch studies with some of the 

 diseased and healthy trees in the Vineland orchards. C. A. Schwarze 

 of the department of plant pathology was assigned to assist in this 

 phase of the work. The behavior of yellows trees is so similar to 

 that of healthy trees that have been girdled in any way or whose 

 normal growth has been inter f erred with by weather, insect or dis- 

 ease injuries that a study of the translocation of starch in normal 

 and diseased trees appeared to be a logical line of investigation. 

 Premature Ripening of the Fruit 



It is a well known fact that girdling causes a premature ripening 

 of the fruit, which is also a symptom of peach yellows. Therefore, 

 it was considered advisable to make certain comparative starch tests 

 on leaves from mechanically girdled trees, winter-injured trees, yel- 

 lows trees and little-peach trees. All these tests showed that the 

 starch was not completely transferred at night but that much re- 



