MARKET DISEASES OF FRUITS AND VEGETABLES 27 



Core Rot 



(Penicillium, Alternaria, Rhizopus, Physalospora, and Fusarium) 



Apples that look sound externally are sometimes decayed at the 

 core. The condition is due to infection by some of the common rot- 

 producing fungi following codling moth or less frequently injury 

 by the lesser appleworm. Core rot sometimes follows cracking 

 at the calyx end or is associated with the condition, seen occa- 

 sionally in Delicious, Grimes Golden, and a few other varieties, 

 in which open calyx tubes furnish a passageway from the outside 

 into the seed cavities. It was found more commonly on apples 

 washed by submersion methods that permit infected washing solu- 

 tions to penetrate into the core. Core rot is generally not a major 

 cause of loss. 



Cork (Boron-Deficiency Cork) 



The term "cork" as used here applies to those symptoms on 

 apples brought on by boron deficiency. There are two phases of 

 this disease on the fruit: namely, external cork, characterized by 

 surface spots, and internal cork, characterized by lesions in the 

 flesh. 



The external-cork symptoms of boron deficiency may be mani- 

 fested within 2 weeks after the petals fall or may appear first as 

 late as 8 weeks after bloom. The spots appear water-soaked at 

 first; then they rapidly turn light brown and become wrinkled, 

 and droplets of sap exude over the surface. The exudate dries, 

 becomes hard and brittle, and is lost through weathering. The 

 affected areas are */2 to 1 inch across and round to irregular in 

 shape and have rounded margins. There may be one or more 

 lesions on a fruit. In general the lesions are superficial, but 

 they may extend to a depth of y 16 inch or more. As the fruits 

 develop, the affected areas crack and corky tissue develops, giving 

 the appearance of severe spray injury such as sulfur burn. Apples 

 seriously affected with external cork frequently drop before reach- 

 ing maturity, and those remaining on the tree are likely to be 

 deformed. 



Internal-cork symptoms are confined to corky spots occurring 

 anywhere in the flesh between the skin and the seed cavity. 

 Deep-seated spots around the core line, often accompanied by 

 a browning of the core tissue, are the most positive symptoms of 

 internal cork. In moderate cases the spots are most likely to be 

 found in the stem end of the fruit, but in severely affected apples 

 the spots may occur throughout the flesh. In cross section cork 

 appears as patches of dead brown tissue, often in close association 

 with the vascular strands, or bundles that conduct food and 

 water through the fruit (pi. 4, E, F). 



Whether external or internal cork develops depends upon the va- 

 riety of apple and the date at which the disease starts. When the 

 disease is initiated within 6 to 8 weeks after the petals fall, the va- 

 riety largely determines whether the lesions will be predominantly 

 external or internal. In New York (19) under the conditions just 

 mentioned, Macoun, Baldwin, Rome Beauty, Northwestern Green- 

 ing, Jonathan, and Woifriver develop mostly external cork, but 

 some internal cork may occur. In Fameuse, Ben Davis, Cortland, 



