RASPBERRY DISEASES 417 
though most dving 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 vet 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. Bul. 108: 3-29. 1912. 
SPUR-BLIGHT 
Caused by Mycosphaerella Rubina (Pk.) Jaez. 
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 
2E 
