APPLE DISEASES 



135 



HYPOCHNUS LEAF-BLIGHT 



Caused by Hypochnus ochroleuca Noack 



It is in the humid regions of the Appalachian Mountain 

 valleys that Hypochnus leaf-blight is most destructive. The 

 disease is known, however, from Maine 

 to Florida, and is most common in 

 North Carolina, Florida, Alabama, 

 Georgia and West Virginia. The 

 pathogene was probably introduced 

 from Brazil, and is known to attack 

 the apple, pear, quince, snowball 

 and lilac. 



Symptoms. 



The chief damage is wrought 

 through the loss of leaves. Affected 

 trees are devitalized, and while twigs 

 are killed, this is an indirect injury 

 through the effects of the disease on 

 the foliage. The disease is, then, 

 principally a leaf-blight. From a 

 distance the symptoms are similar 

 in appearance to those of fire-blight, 

 but Hypochnus leaf-blight is clearly 

 distinguished as follows : (1) affected 

 leaves droop and are matted to- 

 gether, a character not exhibited by 

 fire-blight; (2) small sclerotia are 

 present on twigs adjacent to diseased 

 foliage (Fig. 36) ; these sclerotia are 



white when young, but are cinnamon- apple-twig. 



brown in color when mature; they 



are roundish or oblong and measure one-eighth of an inch or 



less in diameter; (3) accompanying the sclerotia are found 



