144 DISEASES OF ECONOMIC PLANTS 



plum, like that of the peach, usually causes but slight in- 

 jury. See peach. 



Root rot, armillariose. See p. 173. 



Bacteriose. See peach. 



Die back, valsose. See peach. 



SMALL FRUITS 



BLACKBERRY 



Leaf spot (Septoria ruhi Westd.). — Upon the leaves 

 of blackberries, raspberries, and dewberries small spots 

 frequently appear, having a central region white or ashen 

 in color, and the border brown or often of reddish tint. 

 These spots are about 3 mm. in diameter. Close examina- 

 tion of the central ashen region, especially with a hand 

 lens, reveals exceedingly small, Ijlack pycnidia scattered 

 throughout. 



While this disease is exceedingly common and of wide 

 distribution, it does not often develop an epidemic and 

 usually does but little injury, though its damage has been 

 estimated as high as 20 per cent in Florida and Ohio. No 

 treatment has yet proved of sufficient value to warrant 

 its use. 



Anthracnose {Gloeosporium venehmi Speg.). — The an- 

 thracnose is one of the most serious diseases of this crop. 

 For description and treatment see raspberry. 



Crown gall. See raspberry. 



Orange rust (Gymnoconia inter stitialis (Schlecht) Lagh.) 

 — In the early spring the under sides of the leaves of black- 

 berries and raspberries often present a livid red or orange 

 color. On walking through a region so affected the shoes 



