WINTER INJURY IN NEW HAMPSHIRE- -A GROWER SURVEY 



William G. Lord 

 Extension Specialist, Fruit 

 University of New Hampshire 



Winter injury to the roots of apple trees is certainly 

 not a common occurrence in New Hampshire, since an adequate 

 snow cover usually protects tender tree roots from extreme 

 low temperatures. However, throughout much of southern 

 New Hampshire in the winter of 1978-79 snow cover was light 

 and bare wind-blown spots were commonplace. Added to this 

 were low soil moisture levels and long, uninterrupted periods 

 of very cold temperatures - -all the ingredients necessary for 

 root injury. 



The symptoms of severe injury have been well detailed. 

 At about bloom, leaves and blossoms on the affected trees 

 wilt and die. On less severely affected trees, the leaves 

 wilt but seem to recover and injury to blossoms is less severe. 

 New leaves develop and although the tree sets a very light 

 crop and makes no growth, at least the tree is alive. Dam- 

 age of these 2 types is easy to assess and tree crop losses 

 can be accurately and easily determined. However, low level 

 inj ury- - injury that shows up as reduced tree growth, poor 

 leaf color, and reduced set and yields--is difficult to assess 

 and, I feel, tremendously underestimated. 



This Fall a grower survey was initiated to determine the 

 extent of injury and to correlate the incidence of injury to 

 site, rootstock, variety, etc. The following conclusions can 

 be made based on the survey replies: 



1) Rootstock had no effect on the incidence of tree 

 injury. Injury was reported on all the major 

 rootstocks in use in New Hampshire- - seedling , M-106, 

 M-7, M-26, and M- 9/MM- 106 interstems . Where more 

 than one rootstock was present in a particular block 

 showing injury, all rootstocks showed injury. 



2) Tree cultivar likewise (and expectedly) had no 

 effect on the incidence of injury. 



3) Affected trees ranged in age from 1-year-old semi- 

 dwarfs to 60+year-old standards. Again, no correla- 

 tion existed between age and injury. 



4) Herbicide program effects on tree injury are not so 

 clear-cut. It would appear from the grower responses 

 that the majority of sites reporting injury had no 

 herbicide application in 1978, indicating that per- 

 haps there was a slightly greater incidence of injury 

 in blocks where no herbicides were applied. However, 

 it seems more probable that this simply reflects the 

 smaller number of growers who use herbicides rather 

 than any correlation to injury. 



