of several diseased 6-year-old trees. After 3 years' further 

 growth, crowns produced on these trees by the healthy scions 

 are larger than crowns on all-diseased 9-year-old trees. R00I 

 systems have become vigorous and healthy even though they wer< 

 originally small and unthrifty. Roots of the all-diseased 9- 

 year-old trees are still in poor condition. This recovery of 

 the root systems of grafted trees, unaccompanied by recovery 

 of the diseased portion of tops, further suggests that it is 

 loss of foliage that causes the other symptoms (fig. 3). 



Conclusions 



Premature defoliation is one of the most characteristic 

 symptoms of chlorotic dwarf of eastern white pine. The nee- 

 dles formed the previous year are prematurely shed during 

 the growing season, leaving only the newly produced chlorotic 

 stunted foliage. Although the cause of this malady remains 

 unknown, this experiment shows that artificial defoliation 

 of healthy young white pines can cause symptoms similar to 

 those displayed by chlorotic dwarf trees and current foliage 

 is more important to shoot growth than old foliage. 



Leon S. Dochinger, plant pathologist 

 Forest Insect and Disease Laboratory 

 Delaware, Ohio 



6- 



