134 Journal of Agricultural Research voi. xii, no. 3 



York Imperial apples and has also occurred on the Gano and the Esopus 

 varieties. The disease has been under close observation for several years 

 at Wenatchee, Wash., and in the summer of 191 6 a careful study was 

 made of it in orchards at Staunton, Va. In the latter case the disease 

 v\ras found only on York Imperial apples. It could not be correlated 

 with any peculiar soil conditions, but was found decidedly worse on trees 

 that were lightly loaded than on those with a medium or heavy crop. It 

 was much worse on the south side of the tree than on the north side and 

 slightly worse on the east side than on the west. It occurred almost 

 exclusively on apples well exposed to sunlight, always on the blush side 

 of the fruit, and always on fruit surfaces that would receive the oblique 

 rather than the direct rays of light. The spots were similar in appear- 

 ance to cork, but, instead of being scattered over the apple, were often 

 located in a crescent-shaped line at the edge of the blush surface of the 

 fruit. In some cases there was a definite ring almost entirely surrounding 

 the point which received the most direct sunlight (PI. 5, F, G). The 

 skin of the apple was alwa3^s normal, and the corky tissue beneath was 

 usually indicated by surface depressions. While it seems probable that 

 Yorkspot is in part an effect of drouth, its occurrence is undoubtedly 

 greatly influenced by sunlight and possibly by soil conditions and other 

 agencies. 



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 drouthspot 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. Blister 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. 



SUMMARY 



(i) Bitter-pit and Jonathan-spot are distinguished from rosy-aphis 

 stigmonose, drouthspot, cork, and blister. Bitter-pit usually appears 

 first as spots of dead, brown tissue in the subepidermal portion of the 

 apple. These spots are associated with the terminal branches of the 

 vascular bundles and in later stages of the disease the browning often 

 follows the vasculars deep into the flesh of the apple. Rosy-aphis stig- 

 monose is characterized by similar brown spots in the subepidermal region 



