Nov. IS, 1919 



Nature and Control of Apple-Scald 



219 



some forcing agency, such as heavy irrigation, that has apparently ren- 

 dered both large and small apples more susceptible to the disease. 



Table III. — Effect of orchard irrigation upon the development of scald iri storage: 

 Experiments with Grimes apples at Wenatchee, Wash., igi8 



Kind of 

 storage. 



Cellar. 



Air-ccx)led. 



Cold. 



Irrigation. 



(Heavy 

 Light 

 Light followed by 

 heavy 



(Heavy 

 Light 

 Light followed by 

 heavy 



(Heavy 

 Light 

 Light followed by 

 heavy 



Percentage of scald. 



Experi- 

 ment A. 



83 



50 

 59 



40 

 69 

 23 



57 



Experiment B. 



Apples 

 2K inches 



and 

 smaller. 



92 

 23 



42 

 14 



53 

 6 



Apples 

 zH to 3 

 inches. 



56 

 19 



79 

 27 



Apples 

 3 toaM 

 inches. 



90 



15 



64 



5 



75 

 28 



Apples 3K to 

 3% inches. 



73 

 No apples. 



75 

 No apples. 



61 

 No apples. 



RELATION OF TEMPERATURE TO THE OCCURRENCE OF APPLE-SCALD 



The temperature relations of apple scald have been rather fully dis- 

 cussed in earlier reports (5). The rate of scald development increases with 

 a rise in temperature; between 0° and 20° C. each rise of 5° hastens the time 

 of scald appearance by two to six weeks, the greatest contrast occurring 

 between 5° and 10° and the least between 15° and 20°. At 0° scald does 

 not become evident. The apples become latently or potentially scalded 

 but give little evidence of it until removed to a warmer temperature. At 

 temperatures of 25° and above it has not been found possible to produce 

 apple-scald, although other physiological troubles, such as internal break- 

 down, have developed all the more rapidly at these temperatures. Scald 

 has been greatly delayed and in some cases apparently entirely prevented 

 by bringing apples out after four or five weeks in commercial cold storage 

 and giving them a thorough airing for 24 hours at a temperature of 22°. 

 The hypothesis that scald is due to the accumulation of apple esters may 

 furnish at least a partial explanation for the peculiar effects of the higher 

 temperatures. The fruit esters are in general quite volatile, and their 

 rate of vaporization is greatly increased by a rise in temperature. It 

 seems possible that the slight increase in the rate of scald development 

 in passing from 15° to 20° and the absence of the disease at 25° and 30° 

 may be partly if not entirely due to the greater vaporization of the harm- 

 ful products at these higher temperatures. It should not be overlooked, 

 134794°— 19 4 



