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In a 5-year study of common rootrot of wheat in rotations at Indian Head, Saskatchewan, disease ratings were recorded three times each crop season and isolations were made to determine percentage of infection by Helminthosporium sativum and Fusarium culmorum. Wheat preceded by 0, 1, 2, 3, and 5 years of crops not susceptible to H. sativum had 68, 64, 37, 34, and 14 per cent, respectively, of H. sativum infected plants. Corresponding disease ratings for the same years were 28, 27, 22, 17, and 13 per cent, respectively. F. culmorum was isolated frequently from wheat in some of the rotations and it no doubt contributed to increased disease ratings. Oats in the rotation may be a factor in ensuring survival of this pathogen. Common rootrot in wheat may be lessened by using a comparatively long rotation.
R. J. Ledingham (Sat,) studied this question.