Fungicide and Cultivar Management of Leaf Spot Diseases of Winter Wheat in Western Canada.

A complex of leaf-spotting diseases-tan spot, the Septoria complex, spot blotch, and powdery mildew-are frequently observed on winter wheat in western Canada; however, there are few studies indicating varietal differences in reaction to these diseases or the benefit of fungicide application. To determine the benefit of varietal improvement and multiple fungicide treatments and application timings, field experiments were conducted at six site-years in western Canada. Two cultivars varying in reaction to leaf spot diseases were used in combination with fungicide treatments. Disease severity ranged from trace to 64% of the combined flag and penultimate leaf area diseased, differed between cultivars, and was reduced from the check by some fungicide treatments. Yield improvement by fungicide treatment varied from 3.3 to 13.2% greater than the nontreated check. At two site-years, the split application of two half rates of fungicide resulted in the greatest yield; however, in both cases, the yield benefit did not differ from a single application at the flag leaf growth stage. Cultivar selection and fungicide use under environments conducive to disease are beneficial components of an integrated leaf spot disease management program for winter wheat in western Canada.

Black Point Reaction of Durum and Common Wheat Cultivars Grown Under Irrigation in Southern Saskatchewan.

Six durum (Triticum turgidum L. var. durum) and six common (T. aestivum L.) wheat cultivars were compared for reaction to black point under irrigation at two locations in southern Saskatchewan in 1990 to 1992 and 1994. There were individual varietal differences in black point levels within each of the species. The Canada Western Soft White Spring wheat Fielder was the most susceptible and the Canada Western Red Spring wheat Katepwa was the most resistant to black point. The location-cultivar-year interaction was a significant source of variation and a crossover cultivar-environment interaction was significant, suggesting that rank order of cultivars differed with environment. The durum wheat had significantly higher black point levels than the common wheat cultivars in three of the seven environments conducive to black point, two of which were in 1992, and had high overall black point levels. This greater black point severity on the durum wheat cultivars might have been due to cool, wet weather conditions and frosts during seed development that delayed ripening.