132 Journal of Agricultural Research voi. xii, No. 3 



only, there is usually no external marking to indicate the disease; but 

 when the outer pulp tissue is affected, depressions occur over the dead 

 spot, and the apple becomes more or less roughened or corrugated (PI. 

 5, A, B), The development of the disease in the case of these corrugated 

 apples is similar to that of drouthspot in many respects. It appears first 

 as reddish stains on the surface of the apples, and these stained areas 

 may gradually become water-soaked and covered with a sticky yellow 

 ooze. Later the skin regains its normal color, but large areas of dead, 

 brown tissue are left in the pulp. 



Apples affected with cork are sometimes also affected with a condition 

 known locally as "apple-blister." The trouble first appears as slightly 

 raised brown or reddish spots on the skin of the apples (PI. 5, E). The 

 center of the raised portions is very hard and corky, but only the outer 

 epidermal layers are involved. As the apple develops, the blisters crack 

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

 The later stages of blister have usually been found on apples that were 

 also affected with cork, but blister appears 'early in the spring, very 

 often becoming evident as soon as the petals have fallen. 



Troubles identical with cork, or very similar to it, are quite widely 

 distributed. They have been observed by the writers in the Wenatchee, 

 Entiat, Spokane, Okanogan, and White Salmon districts of Washington, 

 in the Willamette and Hood River Valleys of Oregon, in the Okanogan 

 district of British Columbia, in the Champlain Valley of New York, and 

 in various apple sections of Virginia and West Virginia. It is evident 

 from McAlpine's reports {9-12) that the disease is of considerable 

 importance in Australia. 



McAlpine's {9-12) photographs indicate that he included the disease 

 under the name "bitter-pit." Lewis {8) included " corerot " and " dry rot " 

 as forms of fruitpit or bitter-pit. Allen (j) referred to the disease as 

 "fruitpit." Mix {14) has very carefully distinguished between cork and 

 bitter-pit. In British Columbia the disease is known as " malformation " 

 and in Washington as "dryrot." A trouble known in Virginia as "York- 

 spot," or "punky disease" {16), and in California as "hollow-apple" 

 are apparently very closely related to cork. 



The losses from the disease are usually local, but sometimes severe. 

 At Entiat, Wash., in 1916, two carloads of apples from one 20-acre 

 orchard were rendered worthless on account of cork. On the lower flats 

 of the Okanogan Valley in British Columbia it is regarded as the most 

 serious of all apple troubles, and in certain sections of the Hood River 

 Valley, Oreg., it was the cause of considerable annual loss prior to the 

 introduction of systematic irrigation. 



The cause of cork is not known. Allen (j) has reported that fruitpit 

 is worse on trees in a dry soil or in a soil lacking in organic matter. 

 The disease is apparently not produced by fungi or insects. The 

 writers have made repeated attempts to isolate an organism from the 



