CHAPTER IV 

 BLACKBERRY DISEASES 



THERE 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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