VEGETABLE AND FIELD CROPS 281 



confusion in diagnosis referred to above. L. R. Jones,' who 

 studied blacldeg in the field in Germany and England and 

 what appeared to be the same disease in Vermont, described 

 it essentially as follows: The earliest conspicuous symptom 

 was that the diseased plants were slightly below normal 

 size, of a paler or yellowish green color, the lateral branches 

 and petioles becoming more erect and the leaf blades curv- 

 ing upward, giving the entire plant a narrowed aspect. 

 The lower leaves in the meantime have possibly shriveled 

 and died. The stem was more or loss browned or blackened 

 from near the surface of the soil downward. In extreme 

 cases the discoloration was visible 2-3 cm. above the 

 soil. The tissues of the discolored part died, and the softer 

 parts decayed. Usually the seed tuber also was rotted. 

 Rot of the resultant crop of tubers has been reported from 

 Germany, but was not observed in Verinont. 



A disease nearly related to this has ijeen described by Har- 

 rison as due to Bacillus solanisaprus. 



As yet there is little definite knowledge concerning means 

 of distribution or prophyla.\is. Until more definite knowl- 

 edge obtains it is well to avoid badly diseased localities 

 and seed potatoes from diseased regions and to give heed 

 to the general suggestions under soil diseases. 



Potato Spraying 



The spraying of potatoes, as mth other crops, should not 

 be directed or planned to meet merely one of the diseases, 

 but rather to give the plant the best possible protection 

 against all of its enemies. The chief enemies to be met are 



' Jours, L. K., Vt. Aizr. Exi). Stii. Rpt. 19, p. 259, .iiid U.S. Dcpt. Agr. 

 Bur. Plant Indus. Bui. S7, p. 17, 1905. 



