390 Report op the Horticulturist op the 



Injurious Effects. 



The infested leaves frequently turn yellow and drop prema- 

 turely, so that it is not uncommon in August to see a large pro- 

 portion of the new growth leafless, or in case of Yerj severe 

 attacks the tree may lose nearly all of its foliage before Sep- 

 tember. Without the help of the foliage it is unable to properly 

 ripen its wood, and in such instances, especially when it has 

 borne a heavy crop of fruit, it goes into the winter in an enfeebled 

 condition and is liable to be severely injured or even killed by 

 the winter. The leaves may begin to drop to a considerable 

 extent as early as July, but usually the loss from dropping is 

 not serious before August or September. 



The disease frequently checks the growth of plum and cherry 

 nursery stock so much that it is diflScult to bud them in August. 

 It also interferes with the growth of the budded trees. See An- 

 nual Report of this Station, 1898, 688-693. 



The nature of the leaf-spot is such that the disease may pass 

 unnoticed or attract little attention unless it causes the leaves to 

 drop badly. Should the loss of foliage not exceed five or ten per 

 cent, a person unacquainted with the disease would be apt to 

 think that the few leaves which dropped from time to time did so 

 as a result of natural process of ripening rather than because 

 they were attacked by the leaf -spot fungus, and failing to realize 

 the danger of serious loss from this trouble he would take no 

 precautions to prevent the progress of the disease. 



Many fruit-growers do not realize as they should how essential 

 healthy foliage is to the vigor, longevity and productiveness of 

 trees. It is too often the case that a loss of five or ten per cent, 

 of the foliage causes little anxiety, yet this means a loss of five or 

 ten per cent, in the productive power of the tree. It is in the 

 leaves, or other green portions of the plant, that the compounds 

 are formed which are used to sustain life, to support new growth 

 of wood, foliage or fruit, and to develop the fruit buds for another 

 crop. The roots gather crude food materials from the soil, other 

 material is supplied by air, and then with the help of sun-heat 

 and sunlight, in the green portions of the plant, these are formed 



