The Plum. 85 



103. Plum pockets or bladder plums. The plums native 

 to America are often attacked by a fungus {Exoascus [Ta- 

 phrina] Fruni), that causes the young fruits to swell up in a 

 conspicuous and abnormal manner, assuming at first a gray 

 color which later changes to brown or black. Affected fruits 

 are destroyed and finally fall. The disease also affects the 

 leaves and young stems, causing similar distortions. It 

 does not, however, appear to spread much from tree to tree, 

 and is mostly confined to a few varieties. 



Preventive measures. Watch should be kept for the ap- 

 pearance of the disease in spring and early summer, and all 

 affected fruits and leaves should be destroyed. Spraying 

 trees inclined to the disease with Bordeaux mixture as soon 

 as the foliage appears in spring will doubtless tend to pre- 

 vent the attack. Varieties found specially susceptible to 

 the disease should be discarded. 



The foliage of the plum is also sometimes injured by the 

 shot-hole fungus (130). 



104. Propagation of the plum. Various stocks are used 

 in propagating the plum. In localities where the Domes- 

 tica species succeeds, the Myrobolan stock {Primus myro- 

 holana) is much used and is generally satisfactory except on 

 light or otherwise unfavorable soils. 



Seedlings of Primus angustifolia are much used in the 

 southern states, but have the objection of suckering from 

 the roots. The Marianna plum, which is supposed to be 

 of the Myrobolan class, and which grows readily from cut- 

 tings in the south, is also used to some extent. The most 

 satisfactory stock for the plum, at least in the northern 

 states, is undoubtedly seedlings of the Americana plum. 

 The peach was at one time considerably used as a stock for 

 the plum, but has now been nearly abandoned. 



