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 immune; (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 temperature 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, preventing 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 be planted to take care of the excess moisture in the autumn. Such a crop would be particularly desirable following a dry summer. (4) Where irrigation is practiced, the operation should be discontinued in time to allow maturation. (5) The heavy application of nitrogenous fertilizers should be avoided except early in spring. (6) Low, wet soils should be thoroughly tile-drained. (7) Trunks and limbs of trees susceptible to sun - scald should be sprayed or painted with whitewash in the fall or early winter. This method seems more feasible than shading with a board.

But with all these precautions some injury will doubtless occur. Where frost cankers are developed, the injured bark should be removed and the wound treated as described on page 54.

The protection of the buds and blossoms from the action of spring frosts has been shown to be practicable. Orchard - heating is entirely possible and is practiced with profit in the West, and it is recommended for other regions. To combat frost, considerable preparation is necessary and the initial investment is large. The average cost an acre each year for heating is from $10 to $12. Materials such as coal, wood, crude oil, straw or rubbish of any kind are used as fuel. The weather conditions must be thoroughly understood in order to carry on the work successfully.

References

Mix, A. J. Sun-scald of fruit trees a type of winter injury. Cornell Univ. Agr. Exp. Sta. Bul. 382: 237 - 284. 1916. (Bibliography.)

Chandler, W. H. The killing of plant tissue by low temperature. Missouri Agr. Exp. Sta. Research bul. 8: 143 - 309. 1913. (Bibliography.)

Grossenbacher, J. G. Crown rot, arsenical poisoning and winter injury. New York (Geneva) Agr. Exp. Sta. Technical bul. 12: 369 - 411. 1909. (Bibliography.)

Grossenbacher, J. G. Crown rot of fruit trees: field studies. New York (Geneva) Agr. Exp. Sta. Technical bul. 23: 3 - 59. 1912.

Reddick, D. Frost injury. New York State Fruit Growers' Assn. Proc. 11:34 - 41. 1912.

Eustace, H. J. Winter injury to fruit trees. New York (Geneva)

Agr. Exp. Sta. Bul. 269: 323-343. 1905. Morse, W. J., and Lewis, C. E. Maine apple diseases. Non-parasitic diseases. Maine Agr. Exp. Sta. Bul. 185: 341-352. 1910. Macoun, W. T. Winter injury to fruit trees. Canada Exp. Farms Rept. 1907-1908: 110-116. 1909. Whipple, O. B. Winter injury to the fruit buds of the apple and the pear. Montana Agr. Exp. Sta. Bul. 91: 35 - 45. 1912. O'Gara, P. J. The protection of orchards in the Pacific Northwest from spring frosts by means of fires and smudges. U. S. Agr.

Dept. Farmers' bul. 401: 5-24. 1910. Stewart, F. C, and Eustace, H. J. Two unusual troubles of apple foliage. I. Frost blisters on apple and quince leaves. New York (Geneva) Agr. Exp. Sta. Bul. 220: 217-225. 1902. Craig, J. Observations and suggestions on the root killing of fruit trees. Iowa Agr. Exp. Sta. Bul. 44: 179 - 213. 1900.