UNITED STATES DEPARTMENT OF AGRICULTURE 



^ttBi^^tO^ In Cooperation with the 



North Dakota Agricultural Experiment Station 



DEPARTMENT BULLETIN No. 1120 



Washington, D. C. PROFESSIONAL PAPER October 26, 1922 



INVESTIGATIONS OF HEAT CANKER OF FLAX.^ 



By C. S. Reddy and W. E. Brentzel, Assistant Pathologists, Office of Cereal Inves- 

 tigations, Bureau of Plant Industry. 



CONTENTS. 



Page. 



Introduction 1 



Anthracnose canker 2 



Heat canker of flax, a nonparasitic type 3 



Cause of heat canker 3 



Heat canker of flax, a nonparasitic type — 

 Continued. 



Preventive measures 15 



Summary 16 



Similar injury to other plants 14 • Literature cited 17 



INTRODUCTION. 



The seed-flax area of the United States coincides closely with the 

 spring-wheat region of the Northwest, composed for the most part of 

 the States of Minnesota, the Dakotas, and Montana. Within this 

 area flax wilt, drought, and Aveeds are the most important limiting 

 factors in flax production. Flax mlt has gradually pushed the center 

 of flax production westward into uninfested areas, while the newly 

 broken prairie sod with its absence of weeds has led it in the same 

 direction. When the production of flax reached this semiarid section, 

 complaints came from the growers that the plants often broke over 

 at or near the surface of the soil, as though whipped off by the winds 

 or gnawed by insects. 



Fortunately for flax production. Prof. H. L. Bolley early became 

 its advocate in North Dakota and devoted the greater part of his 

 time to it for a number of years. He found the cause of flax wilt and 

 developed control measures in the form of seed selection, seed treat- 

 ment, and the development of resistant varieties (1, 2, 3, and 4-)-^ 

 This has helped to eliminate losses from diseases caused by parasitic 

 seed-borne organisms. Further work (4 and 6) explained the cause 

 of one type of flax canker. As this disease was very destructive in 



I The investigations here reported have been conducted in cooperation with the department of plant 

 pathology of the North Dakota Agricultural Experiment Station. The writers wish to acknowledge their 

 indebtedness to Prof. H. L. Bolley for many helpful suggestions in the progress of the work and to Dr . 

 A. G. Johnson for assistance in the preparation of the manuscript. 



* The serial numbers (itaUe) in parentheses refer to " Literature cited " at the end of this bulletin. 



5419— 22— Bull. 1120 1 



