49 



branch becomes the open door for various wood destroying fungi to 

 enter. 



Trunk splitting is perhaps most common upon peaches, cher- 

 ries and plums, but unfortunately, our other tree fruits are not alto- 

 gether free from such trouble. It is believed to be the result of a 

 sudden and severe drop in temperature causing a contraction of the 

 bark and outer layers of wood and that it is most likely to occur to 

 trees that have made a late growth. 



Bark splitting is much more common than trunk splitting and 

 occurs under conditions similar to those which cause trunk split- 

 ting. A warm, moist, late fall, followed by snow and a sudden 

 and marked drop in temperature are ideal conditions to bring about 

 trunk splitting and bark splitting. The age, variety and actual con- 

 dition of the bark and wood of the tree will, of course, determine the 

 extent of the injury. 



Sun scald is a term applied to a type of bark injury in winter. 

 It is most common and severe upon young trees in northern and 

 western fruit districts. It consists of the killing of the bark upon 

 portions of the trunk, and sometimes of the main branches, where 

 most directly exposed to the sun's rays. This injury, therefore, 

 occurs principally to the south side of trees, and is most likely to 

 occur during the late winter when bright days are followed by cold 

 nights. 



Where the trunks of the young trees are short and partially 

 shaded by the branches, such injury seldom occurs. However the 

 trunks of rather high-headed trees can be artificially shaded by 

 laths, pieces of corn stalks, veneer, or even sprayed with whitewash 

 if there is much danger of injury of this nature. 



Collar injury is much more common and serious than sun 

 scald or bark splitting with either apples or peaches. During the 

 past few years extensive injury of this nature has occurred to 

 peaches in nearby districts. 



The term collar in the vocabulary of the nurseryman and the 

 fruit grower, is a term applied to that portion of the trunk of a 

 tree where the bark of the trunk above ground meets the bark of 

 the root at the soil line. 



Upon young trees this is readily detected by the difference in 

 color of the bark. But unless the tree has been grafted or budded 

 at this point, there should be no very marked difference in the bark 

 structure. There generally is, however, a marked difference in the 

 ability of the bark of the trunk and the bark of the root to with- 

 stand exposure to weather. The bark of the root being accustomed 

 to the protection of the soil is likely to be severely injured if such 

 protection is removed by the washing away of the soil or by having 

 it removed in an attempted freeze out of borers. 



The collar of a fruit tree, in fact, is a very critical point in the 

 whole structure of the tree. It is where the freezing and thawing 

 process is likely to be most severe for within a comparatively short 



