THE PLUM LEAF-BLIGHT 63 



does not penetrate deeply into the fruit, and in itself 

 the disease visually causes little direct damage ; but indi- 

 rectly it is often injurious, by making cracks in the skin 

 through which the spores of other fungi get entrance to 

 the pulp of the fruit. Presumably spraying with Bor- 

 deaux mixture will have a preventive effect upon it. 



THE PLUM FRUIT-SPOT 



Professor L. H. Bailey has called attention to a 

 fruit spot affecting certain native varieties of plums in 

 the south (Fig. 32 c). It is caused by a species of 

 Phoma, and is believed to be allied to the black rot of 

 the grape, and to be controlled by the Bordeaux mixture. 



The Plum Leaf=blight 



Cylindrosporium padi 



The leaves of plum and cherry trees are often at- 

 tacked by a fungus which produces a blight that some- 

 times becomes very destructive, causing whole orchards 

 to drop their foliage prematurely, and thus interfering 

 with the normal development of the trees. Small dis- 

 colored spots, generally of a purplish hue, are the first 

 indications shown by the leaves, of the attack. In a 

 short time these spots turn brown, the tissues being 

 destroyed, and later the leaves become yellow, while 

 many of the affected areas separate from the surround- 

 ing portion of the leaf and drop to the ground, leaving 

 holes, which have given the disease the name of ^^ shot- 

 hole fungus." It is also called the leaf-spot disease. 

 Under a lens the brown spots show a few black dots, 

 where the reproductive spores are developing. The 

 fungus is believed to live over winter on and in the 

 fallen leaves. 



Some confusion exists in horticultural and myco- 

 logical literature concerning the nomenclature of this 



