MAINE APPLE DISEASES. 339 



known in America, but which have been found in Maine, have 

 been mentioned and briefly described. As a rule these are not 

 of much economic importance in the State. Similarly a descrip- 

 tion of some diseases, like the bitter rot of the fruit, which occur 

 to a slight extent in the State have been included because these 

 are of great economic importance in other parts of the country. 

 These latter may or may not become factors in Maine orchard- 

 ing, but it seems desirable that all apple growers become familiar 

 with their characters. 



Character and Causes of Apple Diseases. 



If we accept a rather broad definition that disease in plants 

 includes the effect of every unfavorable factor entering into the 

 life of the plant it follows that various agencies of the living 

 and non-living environment may be responsible for the con- 

 dition known as disease. While it is not always easy or con- 

 venient to discuss the disease apart from the cause, it should 

 be kept clearly in mind that the parasite or other exciting factor 

 is not the disease. The latter is the condition induced in the 

 host as the result of the presence of the former, rendering the 

 plant partly or wholly incapable of responding to its environ- 

 ment. Therefore all methods of disease control should be based 

 upon an as extended and as detailed knowledge as possible of 

 the responsible factor or factors regardless of their nature, but 

 it is important as well to be able to recognize the outward mani- 

 festations or signs of the disease upon the host to aid in its 

 identification. The outward manifestations of plant diseases 

 are frequently not apparent until too late to remove the cause 

 and save the plant or fruit. Hence from their character and 

 mode of attack preventative measures must be largely relied 

 upon to prevent losses from plant diseases, particularly those 

 which attack the apple. 



Those diseases which are induced by unfavorable soil and 

 climatic conditions or other non-living agencies are said to be 

 non-parasitic. Those which result from the attacks of various 

 forms of organic life upon the host or from their presence 

 within its tissues arc classified as parasitic diseases. 



This bulletin is concerned with certain non-parasitic diseases 

 and those parasitic diseases of apple trees and fruit in Maine 

 which are produced by fungi and bacteria. For a detailed dis- 



