92 FUNDAMENTALS OF FRUIT PRODUCTION 



tion from the fruit itself, or, as suggested by McAlpine for 'crinkle,' to the failure 

 of the vascular network over large areas. The striking thing about these diseases 

 is the presence, not the absence, of meshes of this vascular network in close 

 proximity to the dead cell areas. 



"In making the above suggestion as to the cause of cork and drouth spot, the 

 writer realizes that the small amount of experimental work done does not warrant 

 a definite conclusion. There is, undoubtedly, much yet to be learned of the 

 real nature of these diseases. 



"Furthermore, it is not intended to advance this theory to explain the cause 

 of true fruit-pit, or stippen, which occurs in a late stage of the fruit's growth and 

 is said to develop in storage." 



The findings of Brooks and Fisher,^^ who also made an extended study 

 of drought spot and cork in apples, in the main corroborate the conclusions 

 of Mix just quoted. They succeeded in producing drought spot experi- 

 mentally by subjecting Winesap trees to a sudden and severe drought 

 when the fruit was about 1 inch in diameter. Furthermore, trees of 

 other varieties accidentally receiving similar treatment through mishaps 

 to the irrigation system produced fruits exhibiting the same condition. 

 It was noted in the course of the investigation that many trees after once 

 producing drought spot fruits continued to bear them in later years, 

 even though suitable soil moisture conditions were provided. This the 

 investigators believed to be due to the loss of many roots when the 

 drought occurred. They found cork, or troubles very similar to it, in 

 many of the apple producing sections of the Pacific Northwest and in 

 New York, Virginia and West Virginia. In summarizing their findings 

 they state: 



"In nearly every case where the disease has been observed either in the 

 East or West, its occurrence in the orchard has been closely correlated with certain 

 peculiar soil conditions ; sometimes an excess of alkali or an out-cropping of slate, 

 but more often a shallowness or openness of the soil. In most sections cork 

 has been most serious when there was a shortage in soil-water supply, either 

 resulting from Ught rainfall or a lack of irrigation. 



"The observations reported above seem to indicate that cork is a form of 

 drouth injury; yet the disease appears to differ from typical drouth spot, both 

 in characteristics and conditions of occurrences. With certain varieties of 

 apples drouth spot can apparently be produced on any soil under conditions of 

 sudden and extreme drouth. Cork seems to be the result of a less severe but 

 more chronic drouth on trees located on certain peculiar soils, especially on soils 

 that are lacking in humus and are not retentive of moisture. Bhster is closely 

 associated with cork and is probably produced by the same agencies. 



"It should be noted in this connection that the harmful effects of drouth are 

 not always in proportion to the degree of desiccation. Other factors must be 

 considered in a study of drouth troubles, and among these are the percentage 

 of harmful substances in the soil water and the general growth condition of the 

 plant."26 



