Some Observations on Winter Injury 



Winter injury continues to take heavy toll of bearing and non-bearing fruit trees, in many sections 

 of the country and the average fruit grovrer is prone to charge off the loss to weather, without analys- 

 ing any of the factors which may have been responsible for the trees being tender to cold, in a degree, 

 to cause such injury: 



Observations covering the past three years in Georgia, North Carolina, Virginia, Maryland, Pennsyl- 

 vania and New York States shows conclusively that much winter kill has been due to incomplete 

 dormancy. 



In the State of Georgia, thousands upon thousands of peach trees were lost this past season due to 

 incomplete dormancy, when snap freezes started in early December, 1945. The very peculiar weather 

 conditions during growing season of 1945, plus a heavy crop, plus heavy arsenical injury combined to 

 cause general defoliation early in the season. All this was followed by abnormal moisture conditions, 

 which in turn caused the tree to start another flow of sap with the results, that trees were in bloom in 

 November in many orchards. Under such conditions the winter injury was inevitable and the distress 

 will continue, in many orchards as a result for the next several years, with trees continuing to die. 



Another source of great damage to crops and trees has been the late spring freezes experienced in 

 April 1944 and 1945. Virginia, Maryland and New York were very hard hit by this type of injury. 



In many sour cherry orchards the loss of foliage, terminal growth and fruit spur was such, that 

 future fruit crops are in doubt for several years to come, in others, the damage has been so severe 

 that the trees failed to recover and are commencing to die \n great number. 



The question now arises, can winter injury be prevented or rendered less fatal. In our opinion 

 there are several basic factors which have a tremendous influence on tree behavior under low temper- 

 atures, and may be enumerated as follows; fertilizing, spraying, cultivating and pruning. All of them 

 are correlated and must be carried on in such manner that the tree will grow in a satisfactory manner 

 and come into dormancy at the proper time. 



Fertilizing is of paramount importance and we feel must be applied in balanced proportions at the 

 proper time and using fertilizers of proper analysis as the orchard may require. In the past it has 

 been customary in many sections to feed the trees only in spring at or near bud swell. In late years, 

 however, many growers are using fall application with beneficial results to tree and crop, making the 

 application after tree has gone dormant or using at such time as the winter cover crop is put in, but 

 in all cases sufficiently late so as not to throw your trees into a secondary or late growth. 



In the opinion of many growers this method of application is ideal, giving the trees an opportunity 

 to pick up food value throughout the winter and early spring when sap comes to the roots. 



Cultivation rates equal in importance and should start early in the spring and stop at such time to 

 insure proper dormancy. Usually July 15th in northern sections and August 15th for more southern 

 conditions give the proper allowance of time. 



Spraying is another controlling factor which wields a tremendous influence on early or late dorman- 

 cy. Spray material of a certain chemical structure will hold foliage on the tree very late and other 

 formula will defoliate and produce very early dormancy. Therefore it is well to use proper formula 

 and time spray schedules with a thought for future behavior of tree foliage. 



Pruning also, has great bearing on seasonal tree behavior and should be practiced in such manner 

 that the tree is not over stimulated, to the point, where it will continue to grow vigorously beyond the 

 time of safety. 



Lastly moisture conditions is the balance wheel of successful operation. Where extreme dry con- 

 ditions of early or midsummer are followed by too much moisture in late season, such as experienced 

 in 1944 and 45, the results will always be a restimulation of the sap flow and a late dormancy can be 

 expected. 



This late dormancy will in most cases carry over into the hard freezing temperatures with disastrous 

 results, particularly in non-bearing trees and those under six years of age, brought about in most part, 

 where culture programs are carried on to force maximum growth. In young orchards the fruit grower 

 should be particular, to slow down growth early enough to have treetj fully dormant before cold weather 

 strikes. Many young orchards fail to produce normal crops or the trees die early from unexplained 

 causes, when in reality the hidden winter injury of the first or second year after planting is responsible. 



To sum up some of the factors for prevention of winter injury the following should be considered : 



1. Physical condition of orchard trees should be checked at blossom time, mid-season and after 

 harvest for foliage, bud set and terminal growth. 



2. Application of fertilizer in correct amounts and analysis at proper time. 



3. Cultivation of orchard to be timed with regard to effect desired. 



4. Keep a careful survey for spray injury to foliage. 



5. Pruning should be carried out at all times to — (1) Ventilate the tree, (2) To induce setting 

 fruit spurs, (3) To promote early normal growth in order that the trees may be ready for early 

 dormancy. 



By following these few simple rules it is possible to have fruit trees go into winter temperatures 

 in good physical condition to withstand average low winter cold without damage to tree or crop. 



It is well to note that relative hardiness of a given variety has not entered into consideration, be- 

 lieving that the hardiness of most varieties spring from parentage and other characteristics of environ- 

 ment as we have discussed and which can largely be controlled by the grower in his cultural practices. 



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