122 NEBRASKA STATE HORTICULTURAL SOCIETY. 



The pathologist may be able to profit by the observations and 

 suggestions of the plant breeder. 



The fruit growers have discovered long ago that certain 

 varieties were self-sterile. If we plant in isolation such varieties 

 as the Wartield strawberry, the Ben Davis apple, the Wild 

 Goose plum, or Kieffer's Hybrid pear, we find they fruit very 

 sparingly, and when planted where the flowers have free access 

 to pollen of other varieties they become leaders of their kind . 

 All these varieties might be suffering from disease and yet the 

 disease might have nothing to do with the failure of fruit pro- 

 duction. To what extent this condition is true among our cul- 

 tivated varieties is perhaps not well enough understood, and 

 the investigator of plant diseases must not overlook these 

 points. 



Diseases are accountable for an immense amount of damage 

 to our fruit trees, and for convenience we may discuss briefly 

 the most troublesome diseases under each fruit. 



DISEASES OF THE APPLE. 



The apple is probably the most important of the tree fruits, 

 especially in eastern Nebraska. We find upon investigation 

 that our apple trees must survive the attacks of about ten or 

 twelve different diseases in order to produce a crop of apples. 

 Of this number I have selected four which seem to give the 

 fruit grower most trouble. They are, apple scab {Venturia 

 chlorospo7-a), cedar rust (Gymnosporangiurn lYlaa'opus), twig blight 

 (supposed Bacillus armjlovorus), and pink rot of the fruit. 



The first two diseases mentioned are discussed in detail 

 in another paper before the society. In regard to the cedar 

 rust, however, I might add that while I have no experimental 

 proof to offer on the subject, I have observed the disease on the 

 leaves of the apple until I am thoroughly convinced that the rust 

 may spread from the Sporangia which are produced by the first 

 stage on the leaves. 



Pink rot is especially troublesome on some varieties of apple 

 in storage. The fungus causing the disease usually obtains a 

 foothold through the ruptures on the surface of the apple 

 caused by scab or other epidermal diseases. It is, however, 



