2 BULLETIlSr 1120, U. S. DEPARTMENT OF AGRICULTURE. 



western North Dakota and' eastern Montana, arrangements were 



made with the United States Department of Agriculture to continue 



the flax-canker investigations as a cooperative project. This paper 



deals with the results obtained under this cooperation, which began 



in 1916. 



Flax canker is a term which has been applied to any injury to 



flax which causes it to break over at or near the soil line. However, 



the symptoms are not always identical in different districts or in 



different years. Explanations of all these symptoms have not been 



obtained. 



ANTHRACNOSE CANKER. 



Anthracnose canker was described by Bolley in 1910 (^ and 5), 

 when he assigned Colletotrichum lini as the cause. Schoevers, in 

 Holland (19), dealt with the same disease and fungus in 1915. 

 Pethybridge and Lafferty (15 and 16) identified this disease in Ire- 

 land, and in 1918 they named the causative organism Colletotrichum 

 linicolum. They stated that the priority of Colletotrichum lini Bolley 

 was not recognized because of inadequate description. T. Hemmi 

 in 1920 (9) described this disease in Japan and stated that a species 

 of Colletotrichum was isolated which when used to inoculate young 

 plants produced a seedling blight with typical anthracnose lesions. 



In 1916 a species of Colletotrichum was isolated from flax seed of 

 a number of varieties grown at Mandan, N. Dak., in 1915. In 

 inoculation experiments it proved to be parasitic on flax seedlings 

 and produced what properly could be called a damping-off seedling 

 disease (PI. I). 



Surveys of the seed-flax area, extending over a period of six years, 

 gave evidence that different types of flax canker are widespread and 

 capable of producing economic loss and in isolated cases are capable 

 of destroying whole fields of flax. Strange to say, during these six 

 years anthracnose canker was not found by the writers in the seed- 

 flax area, with one exception, when it was discovered on young flax 

 about an inch and a half high at Grassrange, Mont., in 1917. 



At the request of the flax-fiber specialist in the Ofiice of Fiber- 

 Plant Investigations a disease survey of the fiber-flax districts of 

 Michigan and Wisconsin was made during the summer of 1920. 

 Anthracnose canker was found to be widespread in the Michigan 

 district. In a number of cases flax beyond the seedling stage was 

 affected. In some instances as many as 60 per cent of the plants 

 showed girdling, with anthracnose lesions in connection with the 

 girdled areas. This condition closely resembled what Bolley de- 

 scribed in 1910 and 1912 (4 ^-nd o) .^The indications are that it is prob- 

 ably a combination of injuries caused by heat and parasitic fungi. 

 The area affected may be determined more by temperature and the 

 resulting physiological effect on the cells ,than by moisture, oxygen, 



