UNITED STATES DEPARTMENT OF AGRICULTURE 



% BULLETIN No. 1029 



Contribution from the Bureau of Plant Industry 

 WM. A. TAYLOR, Chief 



Washington, D. C. 



PROFESSIONAL PAPER 



March 28, 1922 



SEED TREATMENT AND RAINFALL IN RELATION 

 TO THE CONTROL OF CABBAGE BLACK-LEG. 



By J. C. Walker, Assistant Professor of Plant Pathology, University of 

 Wisconsin, and Pathologist, Office of Cotton, Truck, and Forage Crop Disease 

 Investigations.^ 



CONTENTS. 



Page. 



Introduction 1 



Effect of fungicidal treatment in the 

 laboratory upon seed and the seed- 

 borne fungus 3 



Heat and desiccation 5 



Formaldehyde solution 7 



Hot water 9 



Mercuric-chlorid solution 10 



Summary of laboratory seed- 

 treatment experiments 12 



Field trials with treated seeds 13 



Development of the disease in 



the seed bed 13 



Page. 

 Field trials with treated seeds — Con. 

 Relation of rainfall to the de- 

 velopment of the disease 14 



Importance of spread in the 

 seed bed as compared with 



dissemination in the field 17 



Seed-bed trials at Madison, Wis., 



in 1919 18 



Results with treated seeds in 



commercial fields 20 



Importance of disease-free seeds 23 



Summary 25 



Literature cited 27 



INTRODUCTION. 



The black -leg of cabbage, first noted as occurring in America by 

 Manns {7),~ has become one of the most serious and widespread 

 maladies of this crop. Henderson {3) , who, on the basis of his ear- 

 lier studies in Wisconsin, has given the most complete treatise on 

 the disease, demonstrated that cabbage seeds which had been invaded 

 by the causal fungus, Phonia lingam (Tode) Desm., were a common 



1 The major portion of the work reported upon herewith was carried on at the labora- 

 tory of plant pathology of the University of Wisconsin as a cooperative project between 

 the university and the United States Department of Agriculture. Along with this, the 

 writer has had opportunity for field studies in some of the chief cabbage-growing sections 

 in the Eastern, Western, and Southern States. The writer wishes tO' express his appre- 

 ciation to Prof. L. R. Jones for the helpful advice and criticisms received during the 

 course of the investigation and to Dr. W. B. Tisdale and Miss Ruth Tillotson for assist- 

 ance in part of the field observations and laboratory experiments. 



2 The serial numbers (italic) in parentheses refer to "Literature cited" at the end of 

 this bulletin. 



73603°— 22— Bull. 1029 1 



