PLUM DISEASES 385 
Canada. Japanese plums are more liable to show the disease 
than European varieties ; and it is possible that the latter group 
is never affected. See Peach, page 289. 
Crown-GaLL 
Caused by Bacterium tumefaciens E. F: Smith and Townsend 
Bacterial galls occur on the crown and roots of the plum as in 
the case of other fruit-trees. These enlargements are less com- 
mon on this host than on the apple and peach. See Apple, 
page 108. 
Powpery-MILpEWw 
Caused by Podosphera Oxyacanthe (Fries) De Bary 
Sometimes powdery-mildew affects the plum much like it does 
the cherry, but it is far less common and of no economic impor- 
tance. See Cherry and Apple, pages 177 and 113. 
ARMILLARIA Root-Rot 
Caused by Armillaria mellea (Fries) Quel. 
The plum is susceptible to a rotting of the roots which in many 
cases is caused by Armillaria mellea. In the Pacific Northwest 
prune-growers have been losing trees on account of this disease 
for several years. This root-rot is said to do more damage to 
the prune than to any other fruit in the State of Washington. 
Likewise in some sections of Oregon, particularly in the northern 
part of the Willamette Valley, Armillaria root-rot is a very 
serious menace to the prune industry. For a more detailed dis- 
cussion, see Apple, page 96. 
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