2i6 Journal of Agricultural Research voi. xvi, no.s 



As a whole, the results in Table XIII give most remarkably clear-cut 

 and complete evidence that apple-scald can be prevented by the absorp- 

 tion of the gases (other than carbon dioxid) thrown off by the apples 

 themselves in storage. The beneficial effects of the substances used in 

 the experiments described under (A) may have been partly due to their 

 water-absorbing power, but this could hardly be true of those used under 

 (B) and (C) . One of the particularly striking features brought out is the 

 fact that the various substances have had a beneficial effect in direct 

 proportion to their absorbing power. Excelsior greatly reduced the 

 amount of scald, but sawdust entirely prevented the disease. Paraffin is 

 distinctly the most inactive of all the waxes and oils used, and it was the 

 only one that did not furnish practically complete control for the disease. 

 Apple-scald can evidently be prevented by substances having a compara- 

 tively limited capacity for taking up gases if the absorbing surfaces are 

 placed in rather close contact with the skin of the apple. 



NATURE OF APPLE-SCALD 



The foregoing experiments have approached the apple-scald problem 

 from several different angles, and the results give considerable evidence 

 as to the real nature of the disease. Apple-scald is not necessarily an 

 old-age phenomenon, but is due to the long-continued action of more or 

 less abnormal storage conditions, conditions that cause the produc- 

 tion or prevent the elimination of certain waste products. Most varie- 

 ties of apples may be exposed to such unfavorable conditions for 

 several weeks without developing scald and without showing any ten- 

 dency to the disease if later stored under more nearly normal conditions; 

 but they finally reach a certain critical period at which time they are 

 not scalded, yet have developed a tendency to scald that can not be 

 eradicated by removing the agencies that were originally responsible 

 for the trouble. In the experiment reported in Table VIII, B, apples 

 that were held under conditions favorable to scald for eight weeks 

 showed no sign of the disease when removed to a warm temperature 

 for a few days, yet these apples developed scald later, under storage 

 conditions that did not produce scald on fruit that had never been 

 exposed to unfavorable conditions. With apples that have been shifted 

 from one storage place to another it is evident that the conditions 

 existing at the time of the development of scald may not be the ones 

 that are responsible for the occurrence of the disease. 



Apple-scald seldom, if ever, becomes evident while apples are held 

 continuously at o° C. (32° F.), but cold-storage apples may be found to 

 be badly scalded after a few days at a higher temperature. As was 

 pointed out in an earlier paper,^ the real cause of this sudden appearance 

 of the scald is not the sudden change of temperature. The disease 

 already existed, but the cells were unable to carry out their death processes 

 while a temperature of 0° was maintained. 



'Brooks, Charles, and Cooley, J. S. effect of temperature, aerationj and humidity on jona- 

 Than-spoT and scald of apples in storage. In Jour. Agr. Research, v. ii, no. 7, p. 287-318, 23 fig. 

 pl. 33-33. 1917. Literature cited, p. 316-317. 



