248 EXPERIMENT STATION RECORD. 



total yield and 31 per cent in marketable crop, while potatoes grown on clay 

 loam gained 74 per cent in total yield and 68 per cent in marketable crop. 



The spray compounds used in the second portion of the experiments to com- 

 pare with Bordeaux mixture were copper phosphate, dust Bordeaux, and a mix- 

 tux*e designated as 1-2-3, which is a combined insecticide and fungicide contain- 

 ing arsenic in some form. The results in this series were unsatisfactory on 

 account of the appearance of the blackleg disease, described below, and 

 comparisons can not be sharply drawn. All of the experiments, however, 

 showed by the appearance of the plants that the use of these compounds was 

 favorable. None of the compounds appeared to injure the potato foliage in 

 any way and all seemed to exert some tonic effect upon the plant aside from 

 their fungicidal and insecticidal value. 



The blackleg disease of the potato, L. R. Jones {Vermont Sta. Rpt. 1906, 

 pp. 257-265). — This disease, which is said to be well known in Europe, was 

 under the author's observation in Vermont in 1906. His attention was first 

 drawn to it about the middle of July, when the plants were about 10 in. high. 

 The most conspicuous symptom at this time was that the plants were below 

 normal size, of a pale or yellowish-green color, and the leaves were more 

 erect, giving the plant a decidedly narrowed aspect. 



The author is not fully satisfied as to the cause of the trouble, and he presents 

 various theories regarding its possible origin. Among these are the parasitism 

 of a species of Rhizoctonia, bacterial troubles, etc. In addition the author 

 states that an appearance almost identical with blackleg disease was produced 

 by application of Paris green to some of the plants, the amount applied 

 being so great as to become so lodged on the lower parts of the stems as to be 

 plainly visible. 



The leaf-blotch disease of the potato caused by Cercospora concors, L. R. 

 Jones and J?. S. Pomeroy (rermont Sta. Rpt. 1906, pp. 236^257, figs. 3).— The 

 occurrence of the leaf-blotch disease of the potato caused by C. concors has 

 been previously noted (E. S. R., 18 p. 948). 



This disease made its appearance on early potatoes grown in fairly rich gar- 

 den soil about the time when the plants were in early blossom. A close exami- 

 nation of the discolored leaves showed the presence of a fungus covering the 

 spots, the fungus being most conspicuous on the lower surface of the leaves. 

 The spots increased somewhat rapidly, so that by the middle of July most of the 

 lower leaves were affected. In some cases the invaded portions blackened and 

 died, while the rest of the leaf remained a yellowish green, somewhat resembling 

 the appearance caused by early blight. 



A study of the fungus showed that it was C. concors, and in the authors' 

 opinion, while not before reported as occurring in this country, it has doubtless 

 been present for a considerable time. Its occurrence at the same time as early 

 blight and its general resemblance to this disease have no doubt led to the con- 

 fusion of the two diseases. It is believed that the distribution of this fungus 

 will be affected by summer heat and that it will probably not be found south or 

 west of New York. 



Spraying with Bordeaux mixture is recommended as a preventive, and 

 marked differences in varieties regarding resistance to this disease are noted. 

 The early varieties seem to be most subject to it. 



Bitter pit in apples, J. B. Farmer {Roj/. Bot. Gard. Ketc, Bui. Misc. Inform., 

 1907, No. 6, p. 250). — In continuation of reports on the bitter pit of apples re- 

 ceived from Cape of Good Hope (E. S. R., 18, p. 554) the author calls attention 

 to the fact that in badly attacked varieties the disease was not confined to any 

 special region of the apple. All attempts to establish a fungus or bacterial 

 origin have failed, as well as cultural experiments to demonstrate the presence 



