Influence of Foliar Fungicides and Seed Treatments on Powdery Mildew, Septoria, and Leaf Rust Epidemics on Winter Wheat

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Abstract
Three winter wheat cultivars were grown under an optimum crop management system for Pennsylvania at two locations during 1984 and 1985. The seed-treatment fungicide triadimenol and/or a foliar spray of triadimefon and mancozeb were applied for disease control. The foliar spray was applied as a tank mix at growth stage 6 (Feekes scale). Differences in AUDPC and grain yield among cultivars and cultivar .times. treatment interactions were observed. The cultivar Tyler, which had been resistant to powdery mildew before 1984, became that most susceptible of the three cultivars in 1985. Both seed treatment and foliar spray reduced the severity of powdery mildew with the foliar spray contributing to the greatest reduction. In 33% of the cultivar .times. treatment .times. location evaluations, seed treatment and foliar spray combined reduced powdery mildew severity more than either did alone. The combination of seed treatment plus foliar spray reduced Septoria severity and leaf rust severity more than the individual treatments in 25 and 17%, respectively, of the cultivar .times. treatment .times. location evaluations. Foliar spray alone, as well as combined with seed treatment, increased yield in all trials.