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CIRCULAR 659, U. S. DEPARTMENT OF AGRICULTURE 



of Agriculture (3, 20). Discussion here is limited to a relatively few 

 diseases that are especially influenced by harvesting, handling, and 

 storage operations; most of them are not due to fungi but are functional 

 or physiological in nature. 



The storage disease responsible for most of the decay in apples after 

 harvest is blue mold rot, caused by the fungus Penicillium expansion 

 Link. It is primarily a wound parasite and ordinarily some kind of 

 mechanical injury must be present before the fungus can infect an apple. 

 This rot is very soft and watery and has a pronounced musty odor. It 

 gets its name from the bluish masses of spores that appear on the surface 

 of affected areas (fig. 6, A). This fungus is omnipresent wherever apples 

 are grown, and its spores are found in large numbers on the surfaces 

 of apples as they are picked and brought in for packing. As the fungus 

 is ordinarily incapable of penetrating the sound, uninjured skin of the 

 apple, careful handling of the fruit at all times is a prime requisite in 





A 



B 



D 



Figure 6. — A, Blue mold rot, which is soft and watery, has a pronounced musty odor 

 and frequently is covered with bluish masses or spores. B, Very slight bruises, 

 which show prominently on a peeled apple, emphasize need for careful handling 

 at all times to keep the apples from being bruised. 0, Bitter pit, which appears as 

 brownish spongy or corky spots or pits in the flesh just under the skin and usually 

 is most prevalent on the blossom end. D, Jonathan spot, a superficial skin disease 

 that gives the apple a freckled appearance. 



