CHAPTER IV 
BLACKBERRY DISEASES 
TuerE are several troubles with which blackberry-growers 
have to contend. Crown-gall, anthracnose and orange-rust 
are the most serious enemies. Leaf-spot is common, but not 
destructive. The dewberry is severely affected with double- 
blossom in certain localities. For the most part, blackberry 
and raspberry diseases are the same. 
Crown-GALL 
Caused by Bacterium tumefaciens E. F. Smith and Townsend 
Blackberry represents but one of the many plants attacked by 
Bacterium tumefaciens. The galls (Fig. 45) produced are very 
much like those on raspberry, except that at the crown they are 
often larger and frequently occur along the stem above ground. 
The blackberry suffers to a considerable extent from crown-gall. 
The tree fruits, like the apple and pear, may at times outgrow 
the galls, but the bush fruits, such as the blackberry and rasp- 
berry, succumb more readily. It seems that the blackberry, 
like the peach, is more readily infected than some of the other 
fruits. Possibly this is explained on the grounds that bush 
fruits are set relatively close to each other, which feature of 
their culture is more conducive to inoculation and gall-formation. 
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