MARKET DISEASES OF APPLES, PEAKS, QUIKCES 23 



also the condition seen occasionally in Delicious, Grimes Golden, and 

 a few other varieties in which open cslIjx tubes furnish a passageway 

 from the outside into the seed cavities. During recent years it has 

 been found more commonly on apples washed by submersion methods 

 that permit infected washing solutions to penetrate into the core. 



Core rot is of very little commercial importance. {88, 89, 90, 91, 

 lJf2, 152, 170, 226.) 



CORK 



Cork spots are located in the flesh of the apple, often in close asso- 

 ciation with the strands or bundles that conduct food and water 

 through the fruit. Seen in cross section they appear as patches of 

 dead brown tissue much larger than either bitter pit or stigmonose 

 and occur much deeper in the tissues than drought spot (pi. 9, F). 

 When they occur near the core and nowhere else, the only external 

 signs that they exist are a bumpy surface contour and a rubbery 

 feel when the fruit is compressed in the hand. When they occur in 

 the outer part of the flesh, depressions are found over the dead spot 

 and the apple is more or less roughened or corrugated. Affected 

 apples ripen prematurely, but their keeping quality is not otherwise 

 altered. 



Diseases of the cork type are widely distributed. They have been 

 reported from all the important apple districts of Washington and 

 Oregon, from British Columbia, from New York, and from various 

 apple districts of Virginia and West Virginia. The trouble known 

 in Virginia as " York spot " and in California as '' hollow apple " 

 seems to be very closely related to cork. A disease apparently iden- 

 tical with cork has also been reported from Australia under the name 

 of " crinkle." 



Apples affected Avith cork are sometimes also affected with a con- 

 dition knoAvn as "apple blister ", apparently due to the same condi- 

 tions that produce cork but active earlier in the season. The first 

 stage of apple blister consists of raised brown or reddish spots on 

 the skin of the apple; later on, as the apple develops, the blisters 

 crack and scale off, exposing a rough, corky layer that has formed 

 beneath. 



York spot has been found to occur almost exclusively on apples 

 well exposed to sunlight, always on the blush side, ancl always on 

 fruit surfaces that would receive the oblique rather than the direct 

 rays of light. The spots are similar in appearance to cork, but in- 

 stead of being scattered throughout the apple are often located in a 

 crescent-shaped line at the edge of the blush surface. Occasionally 

 there is a definite ring of them almost entirely surrounding the blush 

 surface. The skin of the apple is always normal and the corky tissue 

 beneath is usually indicated by surface depressions. As suggested by 

 its name, this type of injury is very common on York Imperial 

 apples. 



Cork, blister, and other similar forms of injury are all apparently 

 due to physiological drought, though in general to drought less 

 severe and more long-continued than that known to cause typical 

 drought spot (p. 24). These injuries seem to occur most commonly 

 on soils lacking humus and not retentive of moisture. York spot is 

 apparently due to the combined effects of drought, sunlight, and high 



