Circular no. 935 



January 1954 Washington, D. C. 



UNITED STATES DEPARTMENT OF AGRICULTURE 



Relation of Bruising and Other 

 Factors to Blue Mold Decay 

 of Delicious Apples 



By T. R. Wright, associate pathologist, and Edwin Smith, formerly senior horti- 

 culturist, Handling, Transportation, and Storage of Horticultural Crops, Agricul- 

 tural Research Service 



Contents 



Page 



Introduction 1 



Materials and methods 2 



Factors related to bruising 4 



Maturity 4 



Ripeness during storage 5 



Factors related to infection 5 



Bruising 5 



Maturity 5 



Ripeness during storage 8 



Time of inoculation after 



bruising 8 



Page 

 Factors related to decay develop- 

 ment after infection 9 



Maturity 9 



Ripeness during storage 10 



Cooling rate and storage tem- 

 perature 12 



Summary 13 



Literature cited 14 



Introduction 



The blue mold fungus (Penicillium expansum Lk. emend. Thorn.) 

 is the most important decay organism of apples from the Pacific 

 Northwest. Estimates indicate that 65 to 75 percent of the total 

 rot in stored apples is caused by this fungus (8, IS). 1 From these 

 data together with crop production and valuation statistics (11), it is 

 estimated that there has been an average annual loss of $1,134,112 

 in Washington apples from blue mold since 1939. 



The existence of a relationship between bruising and the decay of 

 apples has long been recognized because of the obvious association of 

 decay with badly bruised fruits. However, little work has been done 

 to show the relation between the amount of bruising and subsequent 

 decay development. Most studies of the bruising problem have been 

 concerned with the relative numbers and severity of bruises occurring 

 in the various stages of handling from tree to table (6, 7, 8, 9, 10, 12) 

 and with the direct economic effects of this damage. Fisher (5) 



1 Italic numbers in parenthes* 



268381—53 



rature Cited, p. 14. 



