44 Diseases of Economic Plants 



blight very similar to that of black-rot, though less important, 

 is caused by Coniothyrium fuckelii Sacc.'*'' 



Pacific coast canker ''^' ^^ {Neofabroea malicorticis (Cord.) 

 Jack., Gloeosporiuin) . — The Pacific coast canker, first noted 

 about 1893, is particularly destructive in the Northwestern 

 states and British Columbia west of the Cascade Mountains. 



The bark or sapwood of twigs and larger branches is the 

 seat of infection, but the disease may occur also upon the 

 fruit when in storage. The loss of an entire orchard within a 

 few years has resulted. Young trees, owing to their tender 

 bark, are especially susceptible. 



Upon twigs, cankers in the early stage appear as round or 

 oval, slightly sunken, dark areas which increase but slowly 

 in diameter. As soon, however, as the fungus penetrates 

 into the cambium and sapwood the canker enlarges very 

 rapidly, making its most rapid development through the 

 cambium, and advancing more tardily through the overlying 

 bark. The resulting spots are nearly circular, quite black, 

 and from 5 mm. to 12-14 cm. in diameter. When old, the 

 bark becomes brittle and a definite fissure separates the dead 

 from the healthy portions, indicating cessation of advance of 

 the fungus. The diseased bark eventually falls away, leaving 

 a scar. Branches, or even trees, may be killed by girdling 

 cankers. 



Upon stored fruit the disease appears first as light-brown, 

 circular, rotten spots. These later turn very dark or black, 

 and become depressed, dry, and tough. Acervuli similar 

 to those upon the bark soon develop in concentric circles. 



When the cankers are few, on small trees, excision may 

 be practiced to advantage; when, however, there are hun- 

 dreds of cankers upon each tree, this treatment is manifestly 

 impracticable. Spraying with strong Bordeaux mixture in the 

 fall, after the crop is gathered and again after an interval of 

 about three weeks, is valuable to prevent the formation of new 

 cankers, and has established practical control of the disease. 



Blister-canker ^^"^^ (Nummularia discreta (Schw.) Tul). — 

 Attention in America was first called to this active, parasitic 



