Killing of Plant Tissue by Low Temperature 283 



(even assuming that the cost of one of the sprayings could be deducted 

 since it could possibly be made to control either San Jose scale or 

 peach leaf curl), would be in the neighborhood of $10 or J>15 an acre, 

 so before one would be justified in recommending such a method, 

 it should be tried under orchard conditions for a long enough term 

 of years to be sure that, say in twelve or fifteen years, enough peaches 

 would be saved to justify the expense. There would unquestionably 

 be some years when no benefit would be received in return for the 

 whitewashing. 



Killing Temperature of Peach Blossoms. A considerable 

 amount of effort has been made to determine, under average condi- 

 tions, the temperature at which the blossoms of peaches are killed. 

 Unquestionably there is a considerable difference in the killing tem- 

 perature of bloom in different years. The killing temperatures in- 

 dicated by laboratory experiments will be given in the last part of 

 this paper (Table 51.) Here the temperature at which bloom and 

 young fruit has been killed in the orchard, and the condition which 

 favor the smallest amount of killing will be discussed. During the 

 spring of 1908 a freeze came on April 3rd when the temperature went 

 to 24 F. at Columbia. Phenological notes taken that spring show 

 that the first bloom on peach trees ranged from March 25th to March 

 30th, and full bloom ranged from April 5th to April 8th. The 

 following table gives the percentage of bloom killed by this freeze: 



10 



