UNITED STATES DEPARTMENT OF AGRICULTURE 



J&r'&Ji. 



BULLETIN No. 727 



Contribution from the Bureau of Plant Industry 

 WM. A. TAYLOR, Chief 



Washington, D. C. 



PROFESSIONAL PAPER 



December 18, 1918 



ANTHRACNOSE OF CUCURBITS. 1 



By M. W. Gardner, Scientific Assistant, Cotton, Truck, and Forage Crop Disease 



Investigations. 



CONTENTS. 



Scope of the investigation 1 



The disease 2 



Hosts 2 



History 3 



Geographic distribution 6 



Economic importance 8 



Description 10 



The causal organism 12 



Taxonomy 12 



Morphology and cultural characters 15 



Physiology 18 



Pathogenicity 22 



Relation to other anthracnose fungi 24 



Page. 



Relation of the fungus to the host tissue 24 



Life history of the causal organism in relation 



to the disease 29 



Seasonal development 29 



Local dissemination by water and other 



agencies 34 



Dissemination with the seed 44 



Overwintering 56 



Control i 58 



Spraying 59 



Seed disinfection and crop rotation 60 



Summary 62 



Literature cited 65 



SCOPE OF THE INVESTIGATION. 



Anthracnose of cucurbits is a common and widely distributed dis- 

 ease of the cucumber, muskmelon, watermelon, certain gourds, and 

 a few other cucurbits. It is apparently limited to this family of 

 host plants. 



The disease is caused by the fungus Colletotrichum Jagenarium 

 (Pass.) Ell. and Hals., and is characterized by sunken or discolored 

 lesions on the leaves, stems, and fruits of its host plants. These 

 lesions are not limited in size, and under certain conditions the 



i The data here presented were obtained as the result of a cooperative arrangement between the Bureau 

 of Plant Industry, the University of Wisconsin, and certain cucumber growers during the seasons of 1915, 

 1916, and 1917. The writer, as a graduate student, was designated by the University of Wisconsin to 

 carry out its part in the cooperation, which also extended to Indiana and Michigan under the leadership 

 of W. W. Gilbert, of the Bureau of Plant Industry. Most of the laboratory studies herein reported were 

 conducted in the laboratory of plant pathology of the University of Wisconsin, and the article itself was 

 presented to the faculty of that university in partial fulfillment of the requirements for the degree of doctor 

 of philosophy. 



The writer wishes to acknowledge his indebtedness to Prof. L. R. Jones, of the University of Wisconsin, 

 for supervision and helpful suggestions throughout the progress of this work, and to Dr. W. A. Orton, 

 Mr W. W. Gilbert, and Dr. E. Carsner for their assistance and cooperation. 

 -18— Bull. 727 1 



