APPLE DISEASES 



467 



Africa. The disease is too coniiiion to 

 need a detailed description. It seems to 

 be very variable in appearance. The most 

 common condition is the occurrence of 

 sunken areas one-eighth to one-half inch 

 in diameter, which have somewhat the 

 appearance of bruises on the surface of 

 the apple. (See Pig. 1.) In the early 

 stages the skin is perfectly normal in 

 color, though often retaining the green 

 tint longer than the surrounding tissue. 

 In red apples the spots may be deeper in 

 color for a time than the surrounding tis- 

 sue. Later they gradually turn brown. 

 The skin is usually unbroken in both 

 early and late stages. 



In cutting an affected apple one finds 

 a browning of the tissue just underneath 

 the sunken areas on the surface and simi- 

 lar discolorations are also frequently 

 found scattered through the substance of 

 the fruit. A close examination shows 

 these discolorations are not entirely sep- 

 arated but are associated with the vas- 

 cular system of the fruit, and connected 

 with each other by very fine brown 

 strands of diseased tissue. These internal 

 spots are usually more abundant near 

 the surface of the apple and in most vari- 

 eties are found more numerous toward 

 the blossom end. A larger amount of 

 starch is usually found in the diseased 

 cells than in the surrounding tissue. 



Cause 



Unlike most other diseases the fruit pit 

 is presumably not caused by any organ- 

 ism; at least, no fungi or bacteria have 

 been found associated with these spots. 

 It evidently belongs to a class of so-called 

 physiological diseases. Various explana- 

 tions have been offered by investigators 

 as to the reasons for the formation of 

 the spots of diseased tissue. Among these 

 explanations given by various authorities 

 are the following: Acidity of cell sap fol- 

 lowing excessive transpiration; prema- 

 ture ripening; abundant moisture and 

 high temperature; influence of stock on 

 scion; dry weather before maturity; 

 complete fertilizers: bursting of cells 

 from pressure due to lack of balance be- 

 tween moisture supply and transpiration. 



In the Northwest the disease is found 

 on soils so diverse both as regards char- 

 acter and richness, and varies so greatly 

 in abundance and severity between differ- 

 ent seasons, that the writer is led to the 

 conclusion, on present evidence, that the 

 most important factors influencing its 

 presence from season to season, are cer- 

 tain varying factors of climate which in- 

 duce the disease by acting through their 

 effect upon the balance existing between 

 the moisture content of the soil, the rate 

 of absorption by the roots and the amount 

 of evaporation from foliage and fruit. 



A trouble of the apple also very com- 

 mon in the Northwest usually referred to 

 as core rot is characterized by a prema- 

 ture breaking down of the tissues, start- 

 ing at the core. This is believed by the 

 writer to be closely related in cause to the 

 fruit pit and the factors influencing its 

 presence are considered similar. It must 

 be recognized that among the different 

 varieties of apples the inherent differ- 

 ences in adaptability to certain types of 

 environment and the natural differences 

 in the texture of the fruit gives rise to 

 great differences in susceptibility to such 

 troubles. 



Growers should be cautioned against 

 mistaking the fruit pit for the 'fruit 

 spot," prevalent in the Eastern United 

 States and particularly in New England, 

 which has long been confused with the 

 former. This fruit spot is caused by a 

 fungus known as Cylindrosporium pomi, 

 and can be prevented by spraying, a 

 method which is useless in controlling 

 the fruit pit. So far as we know, the 

 fruit spot does not occur in Oregon. 



Fruit Rot 



Coniotliyriose 

 The rotten spot is circular in uniform 

 tissue, brownish, about the color of the 

 common soft rot, and due to loss from 

 evaporation, the tissue shrinks as the 

 spot ages, leaving the surface much 

 wrinkled. Distributed somewhat sparsely 

 and irregularly over the spot are the 

 fruiting cavities of the fungus. In rotten 

 spots, produced by inoculation, these 

 cavities frequently assume a somewhat 



