RASPBERRY DISEASES 417 



though most dying takes place during the first half of the sum- 

 mer. Other plants which do not die show a wilted and yellowed 

 condition of the foliage. Canes do not always show external 

 signs of the blue-black discoloration. Internally, however, 

 affected canes exhibit characteristic reddish streaks. The roots 

 also may show this internal discoloration. In a single planta- 

 tion every hill may show the blue-stem disease. 



Cause. 



The life-history of the causal fungus, Acrostolagmus caulo- 

 phagus, is -not fully known. It apparently lives in the soil 

 and in some way gets into the plant at a point below the 

 surface of the ground. There is some evidence that entrance 

 is gained through the roots. The mycelium invades the wood 

 ducts profusely. Progress in the roots is slow; however, in 

 above-ground parts the rate of spread, as already indicated, 

 may be from three to six inches each day. The mycelium at 

 times completely plugs the wood-ducts, thus accounting for 

 the wilting, yellowing and death of affected plants. 



Control. 



As yet no experimental data are at hand on which to base 

 reliable recommendations for the prevention of blue-stem. 



REFERENCE 



Lawrence, W. H. Bluestem of the black raspberry. Washington 

 Agr. Exp. Sta. Bui. 108 : 3-29. 1912. 



SPUR-BLIGHT 



Caused by Mycosphcerella Rubina (Pk.) Jacz. 



This disease has been reported only from Colorado and New 

 York. It probably occurs elsewhere. Both black and red 

 varieties of raspberries are affected. In Colorado it is regarded 

 as a very important trouble. It ranks well up with other factors 



2s 



