HEAT CANKER OF FLAX. 



FIELD EXPERIMENTS. 



During the latter part of the season of 1917 a shading experiment 

 was conducted. The shade was provided by two pieces of canvas, 

 each about 6 feet square, stretched horizontally about 3 feet from 

 the ground above the young flax plants. In this experiment canker 

 occurred in neither the shaded nor the unshaded area. However, 

 the experiment did show that methods of shading which would 

 reduce the light to a less degree were desirable. These investigations 

 were temporarily discontinued during 1918. 



In 1919 further experiments were planned and conducted to test 

 the effect on young flax plants of intense sunlight and resulting heat 

 at the soil line. Experiments were conducted also with a view to 

 producing flax canker by artificial means. 



Shading experiments were planned in which partial shade was 

 provided by (1) strips of canvas, (2) cereal nurse crops, and (3) 

 weeds. In these shading experiments the typical plat (Fig. 1) was 2 



NOfPTH 





SPRWe WHE/tT 



o/frs 



FUIX CcT./s) 

 (WILT suscept/ble) 



FL/^X (c.1.13) 

 {wilt RESISr/!NT) 



■J 



-^<- 



jyr/VffEff of^ si//fF/icE 



Fig. 1. — Plan of a typical plat in field experiments conducted at Fargo, N. Dak., in 1919, to determine 

 the cause of flax canker of the nonparasitic type. Rows 3 and 8, marked with an asterisk (*), sown 

 thinly at half the normal rate. Canvas strips 10 inches wide and 1 rod long were placed close to the flax 

 rows marked with two asterisks (**) for shading from about 10 a. m. to 4 p. m., half on sanded area 

 half on area not sanded. 



rods long east and west and 10 feet wide north and south. It was 

 divided into halves by a line extending north and south, and the soil 

 of one of these halves was covered thinly with sand. The plat con- 

 sisted of five rows each of two varieties of flax, North Dakota Resist- 

 ant No. 114 (C. I. 13), a wilt-resistant variety, and Reserve (C. I. 19), 

 a variety susceptible to wilt, and two rows each of flax with one of 

 the cereals, oats, barley, spring wheat, or winter wheat, as a nurse 

 crop. The rows extended east and west, so that each plant would be 

 exposed to the sun's rays during the hottest part of the day and for 

 the longest period possible. There was a 12-inch space between the 

 second and third rows of each variety, and the third row of each 

 variety was sown at half the usual rate. The other rows were spaced 

 6 inches apart. Half of the second row of each variety was shaded by 

 placing just south of it a vertical strip of canvas 10 inches wide and 1 

 rod long. By this means the young plants were shaded from about 



