26 



Twig Blight of Apple. 



APPLE DISEASES. 



Prof. H. R. Fulton, Pennsylvania State College. 



I have been asked to speak on the subject of apple diseases. 

 Fully twenty of these, aiiecting all parts of the apple tree, have 

 come to ni}^ notice in Pennsylvania. Fortunately the majority are 

 only slightly injurious ; several that are very serious in other sec- 

 tions of the country occur very infrequently with us. We can con- 

 sider only the most important apple diseases to-day. 



These diseases, for our purpose, may be classified as fungous 

 and bacterial diseases, and physiological diseases, remembering that 

 bacteria are, after all, merely a special kind of fungi. Those of 

 the first class are caused by living plant organisms of very small 

 size, that may spread from plant to plant ; and these diseases are in- 

 fectious or contagious in character. However, climatic and local 

 weather conditions., as well as other conditions of environment^ may 



