When only current needles were removed, needle chlorosis 

 and shortening were less pronounced. Though removal in July 

 and September reduced shoot growth, effects were most severe 

 in the single tree surviving April treatment. Growth of its 

 shoots was reduced as much as that of the two trees surviving 

 complete defoliation. Presumably old needles were less ef- 

 fective in photosynthesis when current needles were removed 

 in April than when removed earlier. 



Stripping all needles except current ones did not cause 

 any visible disease symptoms and did not affect growth in 

 height (table 2). Thus, in contrast to current needles, old 

 needles apparently contribute little to overall growth and 

 survival . 



Discussion 



Eastern white pine has been artificially defoliated in 



1 / 

 another invest igat ion ._/ Other species that have been so 



treated include jack pine (P. banksiana Lamb.),_/ jack pine 

 and Scotch pine (P. sylvestris L.),^/ and tamarack (Larix 

 laricina (Du Roi) K, Koch.V ^Results obtained agree with 

 findings of this study. That is, complete defoliation is 

 usually fatal and needles of the current year are more im- 

 portant for shoot growth than older needles. 



Decreased shoot growth and stunted needles that are pro- 

 duced by artificial defoliation resemble symptoms displayed 

 by diseased trees. This suggests that many of the later mani- 

 festations of the chlorotic dwarf disease result from the pre- 

 mature defoliation. This supposition is supported by findings 

 that indicate that chlorotic dwarf symptoms on white pine 

 roots are affected by the condition and amount of foliage.£./ 

 In 1959, healthy white pine scions were grafted to terminals 



17 Linzon, S. N. The effects of artificial defolia- 

 tion of various ages of leaves upon white pine growth. 

 Forestry Chron . 34: 50-56. 1958. 



2/ O'Neil, L. C. Some effects of artificial defolia- 

 tion on the growth of jack pine. Canad . Jour. Bot . 40: 273- 

 280. 1962. 



3/ Craighead, F. C. Some effects of artificial defolia- 

 tion on pine and larch. Jour. Forestry 38: 885-888. 1940. 



4/ Graham, S. A. The effects of defoliation on tamarack 

 Jour. "Forestry 29: 199-206. 1931. 



5/ Report to be submitted to Phytopathology. 



-5. 



