-3- 



of winter injury that occurred during the winter of 1933-34 were: 

 killing of the sapwood in the branches and trunks; loosening and 

 splitting of bark on the trunk; and injury to flower buds and spurs. 



Winter injury to above-ground portions of fruit trees has also 

 occurred since the writer came to Massachusetts in 1955. In the 

 spring of 1956 we found severe winter injury to the trunks and lower 

 scaffold limbs of bearing trees, mainly Mcintosh in several orchards. 

 The bark on the injured tree trunk was split and usually pulled 

 away from the wood. The injury was most predominant on the south 

 side of the tree, but no side was immune. The winter injury appeared 

 to be associated with pruning during late December and early Janu- 

 ary. During the winter of 1956-57 extensive wood injury and injury 

 to both flower and leaf buds occurred on peach trees and to flower 

 buds on sweet cherries and plums. 



Pruning-related injury also occurred during the winter of 1975- 

 76. It was found in more orchards than in 1956 and also occurred 

 in Connecticut and New Hampshire. The trunk injury was associated 

 with pruning done as late as the 3rd week of January in 1976 in 

 some orchards. Cold injury and how it relates to the winter injury 

 in 1975-76 was reviewed by D.A. Kollas in 1978 in Fruit Notes 43(6): 

 1-5. 



This past winter (1978-79) root-kill was the predominant type 

 of injury to apple and peach trees. On peach trees the bark on the 

 trunk at ground level or below ground also was injured. 



The main objective of this article is to have a written account 

 of winter injury in 1978-79 for reference if similar damage occurs 

 in the future. 



Early Studies on Root Damage 



Roots have been found to be the tenderest part of the apple 

 tree although those that have been exposed throughout the previous 

 growing season have cold tolerance equal to the above ground tree 

 parts. D.B. Carrick in New York State (Cornell University Agr. Exp. 

 Sta. Memoir No. 36, 1920) reported that, under laboratory conditions, 

 apple roots frozen in October and November were more tender than 

 those frozen in February or early March. The period of maximum re- 

 sistance to freeze damage seemed to end before last of March. J.R. 

 Magness in Washington State showed that bark of apple roots was 

 killed at temperatures as high as 23° F. in November. ^Root samples 

 taken in early December were killed by exposure to 17° F. 



G.F. Potter in New Hampshire reported that 16° F. was usually 

 critical for roots of 1-year-old apple trees under laboratory con- 

 ditions. Very rapid freezing of roots to 18° F (in a half hour or 

 less) caused more injury than when freezing them so that the roots 

 reached the same temperature after 6 or 7 hours. However, rate of 

 thawing did not affect the severity of the low temperature injury. 



