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 
