APPLE DISEASES 135 
Hypocunus Lear-Biicut 
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- 
brown in color when mature; they 
are roundish or oblong and measure 
Fic. 36. — Hypochnus leaf- 
blight pathogene; sclerotia on 
apple-twig. 
one-eighth of an inch or 
less in diameter; (3) accompanying the sclerotia are found 
