Effects of seeding date and cultivar susceptibility on effectiveness of carbathiin for control of common bunt (Tilletia tritici and T. laevis) in winter wheat in southern Alberta
1994
Gaudet, D.A. | Puchalski, B.J. | Entz, T.
Carbathiin (carboxin) was evaluated in three cultivars of winter wheat artificially inoculated with Tilletia tritici and T. laevis for efficacy as a seed treatment at three rates (0.55, 0.76, and 1.1 g ai/Kg) on eleven seeding dates during 1989-92. The cvs. Norstar and Norwin, were susceptible and highly susceptible to common bunt, respectively, on all planting dates; cv. Sundance was moderately resistant when seeded in mid-September but susceptible when seeded in October. Efficacy of carbathiin for bunt control decreased with late seeding in all cultivars. A carbathiin rate of 0.55 g ai/kg was generally ineffective in controlling bunt, even early-seeded treatments. Environmental conditions which promoted bunt severity reduced the efficacy of carbathiin at the 0.55 ai/kg rate. Incomplete control of common bunt with the 0.55 g ai/kg rate was exacerbated by the high susceptibility of Norwin the later seeding dates. At 0.76 g ai/kg, bunt levels were low in all cultivars except when seeded late. The highest carbathiin rate 1.01 g ai/kg, controlled bunt regardless of cultivar or seeding date. At rates of 0.76 g ai/kg and higher, infection levels were low but variable, likely due to micro-environmental effects on efficacy. The nature of variability in efficacy of carbathiin at the different application rates is discussed and related to conditions in the seed micro-environment.
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