544 SPECIAL PLANT PATHOLOGY 



chymatic mycelium and conidial masses are rosy white. The powdery 

 dry-rot with pink mycelium-Uned cavities is quite characteristic and 

 not easily confused with the other species of Fusarmm found on 

 potatoes.^ 



Scab {Actinomyces chromogenes). — This scab disease is one well- 

 known throughout the United States and also in Europe, although 

 all the cases of scabby potatoes are probably not due to this fungus, 

 as a causal organism. Turnips, beets and mangels are susceptible 

 to the disease while carrots and parsnips are not. The first symptoms 

 of the disease are minute reddish-brown spots on the surface of the 

 tuber beginning usually at one of the lenticels of the tuber and spread- 

 ing rapidly to other tissues, assuming a deeper color and an abnormal 

 corky development over considerable areas. Thus arise the scab-like 

 crusts which have given the common name to the disease. The surface 

 of the tuber frequently becomes cracked to considerable depths. If 

 scabby potatoes are examined immediately after being gathered a fine 

 grayish, evanescent film will be found consisting of extremely delicate, 

 minute, refractive, branched filaments, which break up into bacteria- 

 like cells. Some branches are curved and structures suggesting true 

 spores are produced in certain cells. The writer has found the fungus 

 as minute white specks on horse manure. It has been found to 

 persist in the soil for several years. 



The disease can be controlled by soil treatment, by the adoption of 

 a rational rotation of crops and by planting seed tubers only after they 

 have been treated for several hours with a solution of i ounce of 

 formalin to every 2 gallons of water, or by a solution of corrosive 

 sublimate in water. 



Raspberry {Rubus occid entails, L.) 



Anthracnose {Glceosporlum vcnetum, Speg.). — As this fungus pro- 

 duces injuries to the raspberry and blackberry canes, it was called by 

 Burrill, who published the first account of the disease in 1882, the "rasp- 

 berry cane rust." It is known to occur in New Jersey, Illinois, Texas, 

 Wisconsin, Missouri and other states. 



The fungus attacks both fruiting and non-fruiting canes, or suckers, 



1 Carpenter, C. W.: Some Potato Tuber-rots caused by Species of Fusarium. 

 Journal Agricultural Research V: 183-209, Nov. i 1915. 



