166 MANUAL OF FRUIT DISEASES 



Reimer, F. C., and Detjen, L. R. Double blossom of the dewberry 

 and the blackberry. North Carolina Agr. Exp. Sta. Ann. Rept. 

 34 : 41-50. 1912. 



Cook, M. T. Some diseases of nursery stock. Double blossom of the 

 dewberry. New Jersey Agr. Exp. Sta. Circ. 35 : 24. 1914. 



ARMILLARIA ROOT-ROT 



Caused by Armillaria mellea (Fries) Quel. 



The shoe-string fungus attacks the blackberry among other 

 plants. It is said that considerable injury is done in the Pacific 

 Northwest. (See Apple, page 96.) 



LEAF-SPOT 

 Caused by Septoria Rubi Westd. 



The common leaf-spot of blackberry affects also the rasp- 

 berry and dewberry. It is found in almost every locality where 

 these fruits are grown. While the disease is common, it is not 

 often serious. Rather it is enphytotic, doing but little damage 

 under ordinary conditions. In 1905, however, 20 per cent 

 foliage-losses were reported from Ohio and Florida. 



Symptoms. 



The appearance of this disease is said to vary to a marked 

 extent on different varieties. On some varieties the spots on 

 the leaves (Fig. 46) are light-brown, while on others they are 

 dark-brown. The lesions are comparatively small, measuring 

 about one-eighth of an inch in diameter. The diseased portion 

 is at first purplish, although a brown color is assumed as the 

 affected tissue dies. In old spots the center is whitish, and the 

 border is brownish or reddish. 



Cause. 



The 'causal fungus is Septoria Rubi. It belongs to a group of 

 organisms the life-histories of which are fairly well understood. 



