BULLETTIN 0F THE 



No. 64 



Contribution from the Bureau of Plant Industry, Wm. A. Taylor, Chief. 

 February 10, 1914. 



(PROFESSIONAL PAPER.) 



POTATO WILT, LEAF-ROLL, AND RELATED 

 DISEASES. 



By W. A. Orton, 

 Pathologist in Charge of Cotton and Truck Disease and Sugar-Plant Investigations. 



INTRODUCTION. 



During recent years there has been much doubt and misunder- 

 standing among plant pathologists and observant farmers concerning 

 the group of potato diseases variously referred to as wilt, leaf-roll, 

 leaf-curl, Fusarium bhght, bacterial ring disease, etc., which in 

 different countries of the world appear to constitute problems of 

 increasing importance to practical agriculture. 



This bulletin seeks to clear up the situation and to open the way 

 for more efficient measures of control by differentiating these pre- 

 viously confused diseases and fully describing the methods of diag- 

 nosis. The results afford a strong argument to pathologists for a 

 broader outlook over the field and for international as well as national 

 comparisons of conditions. The fundamental importance of thorough 

 laboratory investigations is not minimized, but the interpretation of 

 results in their relation to the basic principles of plant pathology and 

 to the general problems of agriculture require a better conception of 

 the different environmental influences to which crops are subjected 

 in the several States and in foreign countries. 



To the practical potato grower to whose attention these new potato 

 diseases are brought, the feature of greatest significance will be their 

 effects in impairing the vigor of his seed stock and on the deterioration 

 of varieties. New evidence is presented that large but insidious 

 losses have been suffered from seldom-recognized weaknesses in vege- 

 tative vigor and from diseases transmitted through the seed — losses 

 that threaten to be greater in the future unless active measures are 

 taken at once to secure more vigorous and disease-free strains or 

 varieties through seed selection and breeding. 



NoTjE.— This paper is of interest to plant pathologists; it is suited to the potato-growing sections of the 

 North, West, and South. 



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