110 



MAINE STATE COLLEGE. 



II, Apple Scab, (Fusicladium denclriticum.) 



It is not within the province of the writer to discuss in detail 

 the characteristics of fungi injurious to fruits ; but as no descrip- 

 tion of the disease known as apple scab has heretofore been pub- 

 lished in the reports of the Experiment Station, it may be well to 

 call attention, in a general way, to the nature of this disease. 



All are familiar with the dark colored spots or scabs which 

 appear on some varieties of apples, — notably the Fameuse, the 

 Maiden Blush, and the Baldwin. These spots represent but one 

 stage in the life history of a plant which grows on, and obtains 

 its nourishment from the apple. In other words, apple scab is 

 caused by the attack of a parisitic fungus — Fusicladium dendritt- 

 cum. Its attack is not always confined to the fruit, and it is 

 sometimes the cause of very serious loss to the orchardist. 



The plant is reproduced by means of spores,* which are carried 

 by the wind, and vegetate under favorable conditions. The most 

 vigorous growth is made during cool, moist seasons. The climate 

 of this state seems specially favorable for the growth of the 

 fungus. 



Figure 1 represents the 

 disease as it appears on 

 the fruit. In badly affect- 

 ed specimens the scabby 

 spots are much larger and 

 often cause the apple to 

 crack. The nourishment 

 is all taken from the 

 affected side, and in con- 

 sequence the fruit is de- 

 formed. If the fruits are 

 very young when attacked, 

 they usually wither and 

 fall. 



Fig.l. A Diseased Apple. The f ungus attacks the 



leaves and young growing twigs as well as the fruit. If the 

 attack occurs early in the season and is severe, much damage may 



* The appearance of these spores is illustrated in the report of the Maine 

 Experiment Station for 1S89, page 182. 



