APPLE DISEASES , . 39 



Roots suffer when the temperature is unusually low and the 

 ground is bare. In some of the western states this is common 

 and serious. It occurs more often on trees up to twenty years 

 of age. The whole root-system may be killed, and the injury 

 or death of tissues may extend to the crown. Ben Davis, 

 Northern Spy and Wealthy suffer especially. Trees on crab- 

 stock are said to be affected less than others. 



The above described injuries on the roots, crown, trunk, 

 crotch and branches are regarded as a winter type of frost- 

 injury. Late spring frosts are sometimes troublesome, and do 

 damage to the fruit-buds, blossoms, leaves and young fruits. 

 All parts of a bud are not necessarily killed. Generally only 

 the floral parts are involved, so that the buds will open in the 

 spring and the killing will not be readily observed. Injury to 

 the blossoms is a common form of frost-injury. Affected blos- 

 soms turn brown and die. It is likely that growers sometimes 

 confuse loss of blossoms due to low temperatures with that 

 caused by poor pollination. Young leaves are killed or in- 

 jured at higher temperature than are old, mature leaves. 

 Affected leaves crimp and curl; their upper surfaces are 

 wrinkled and puckered and resemble peach leaf-curl to a 

 certain extent. Heavy frosts at a time when the leaves are 

 partially unfolded bring about the injury. Frost bands on 

 young fruits are familiar to all. Occasionally late frosts occur 

 which do not destroy the set of fruit, but there results a peculiar 

 russeting. In older apples, this appears as a band of varying 

 width entirely around the fruit midway between the stem and 

 calyx-ends. 



Cause of frost-injury. 



It is held by earlier authorities that the various forms of frost- 

 injury arise in different ways. That is, it is thought that 

 crown-rot and sun-scald are different. However, it is now 

 generally agreed that crown-rot and sun-scald are essentially 

 the same, differing only in appearance and in location on the 



