APPLE DISEASES 43 
growing season, will, if a severe winter follows, be seriously 
affected by low temperatures. A dry summer followed by a 
warm, wet fall makes a tree more susceptible to cold than it 
otherwise would be. Late cultivation and excessive nitrogenous 
fertilization forcing late succulent growth tend to an unripened 
condition of the trees, rendering them susceptible to early win- 
ter-injury (crown-rot). Sun-scald, however, is not induced by 
these conditions. The topography, type of soil, and methods 
of orchard management are factors influencing the severity of 
frost-injury. 
Control for frost-injury. 
From the foregoing remarks and discussion it seems advisable 
to reiterate in discussing control the following points with 
reference to winter-injury: (1) that while some varieties of 
apples are more susceptible to cold than others, none are im- 
mune; (2) all parts of a tree are liable to injury, and these 
injuries are referred to according to the part affected, as root- 
injury, crown-rot or collar-rot, black-heart, crotch-injury and 
sun-scald; these are forms of winter-injury, whereas spring 
frost affects the buds, blossoms and young fruits; (3) low tem- 
perature injury is essentially a desiccation-proccess, resulting 
chiefly from the sudden withdrawal of water from the cell 
during a sudden drop in temperature; (4) succulent immature 
tissues suffer more than properly matured tissues; (5) injured 
bark is inhabited by fungi which may enlarge the wound, pre- 
venting it from healing; (6) trees on low, wet soil suffer most ; 
(7) a dry summer acts detrimentally, and if the autumn is wet, 
succulent tissue is developed; (8) injudicious nitrogenous 
fertilization and cultivation also favor winter-injury. 
It is recommended: (1) that in planting, only those varieties 
best adapted to the particular soil and environment be selected. 
(2) Orchards should be cultivated thoroughly in the earlier 
part of the season, but the operation should cease in time to 
allow trees to mature thoroughly. (3) A cover-crop should 
