MORTALITY OF APPLE MAGGOT IN FRUIT IN STORAGE 5 



ture. A satisfactory base should be the time when the temperature 

 of fruit in this position comes within 1° of the air temperature. In 

 these experiments fruit at the center of the basket reached this tem- 

 perature within about 72 hours. 



Refrigeration engineers recognize that there may be some difference 

 in temperature between the exterior and interior of a package under 

 storage. This variation, however, can be practically eliminated 

 through forced circulation of the air. Similarly, there is normally 

 some variation in temperature between packages in different parts of 

 the storage chamber. Under commercial conditions a storage temper- 

 ature of 32° F. usually is understood to carry a 2° differential, or a 

 temperature ranging from 31° to 33°. Most cold storages can operate 

 on a 1° differential by creating sufficient air movement in the chamber 

 and by careful regulation of refrigeration. 6 



Since in the present experiment the fruit temperature varied nearly 

 1° F. between the exterior and interior of the package, the fruit temper- 

 atures maintained were actually 32° to 33°, 36° to 37°, and 40° to 41°, 

 instead of 32°, 36°, and 40°. For the sake of simplicity, however, the 

 temperatures mentioned will refer to the approximate temperature of 

 the air in the refrigeration room unless specifically indicated otherwise. 



EXPERIMENTAL RESULTS 



Detailed data on the individual experimental lots and the results 

 obtained with fruit held at the three storage temperatures are given in 

 table 1. The mortalitv for a given lot was obtained from the number 



100 



50 



25 



DAYS AFTER FRUIT ATTAINED TEMPERATURE OF REFRIGERATION ROOM 

 7 17 27 37 47 57 



■ 



A/ i 



nr 



/ V 



r r>»^-^""(» 



?— <b n ft 



0^ 



i a 







- 



1 1 ' 



S e 



^ 









■ 



/ ^r 













iimI hi 



> i i i 1 i i i i 



iimImm 





iimImm 



,,,,!,,,, 



....!.... 



30 40 50 



DAYS UNDER REFRIGERATION 



Figure 3. — Mortality of the apple maggot after being held for various periods in 

 the refrigeration room at air temperatures of 32°, 36°, and 40° F. 



of larvae that emerged and the number that theoretically should have 

 emerged. This theoretical larval expectation is calculated from the 



ratio of the total number of larvae emerging to the total number of 



. \^ns\ 



e The generalizations appearing in this paragraph are based on statements occurring in a memorandum 

 prepared by Lon A. Hawkins, Bureau of Entomology and Plant Quarantine, U. S. Department of Agricul- 

 ture, dated April 20, 1938. 



