4 FARMERS’ BULLETIN 1641 
Cankers on smooth bark are easily recognized by their yellow- 
ish brown surface color, which contrasts sharply with the grayish 
green color of normal bark. The margin of the canker may be 
slightly raised in some cases, and in others it may have a 
water-soaked appearance, especially on vigorously growing shoots. 
Usually the margin of the canker is fairly regular (fig. 4), but 
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Ficurs 2.—An orchard chestnut partly killed in early spring. It shows very small 
leaves in contrast with normal ones 
sometimes it is irregular. (Fig. 5.) There is less contrast between 
the appearance of the canker area and its margin on slowly growing 
shoots or twigs. 
The cankered areas may be either sunken below or raised above 
the surrounding healthy ine or a single canker may have both 
sunken and raised parts. When the fungus promptly kills the bark 
all the way through to the cambium and into the wood, there results 
