Series/Report Number: COARC2014

Abstract: A replicated field study was established to evaluate the efficacy of fungicides to control common leaf spot in alfalfa seed production fields. Plots were established in a second-year field with a history of common leaf spot. Treatments included 7 fungicides and a water-treated control applied once in early June. Although common leaf spot was not detected in any plots, mild symptoms caused by downy mildew were observed. Significant differences in downy mildew severity, plant height, leaf retention, or seed yield were not observed (P > 0.05) among treatments in this trial. The identification of downy mildew in central Oregon alfalfa seed crops is novel information that can be used by the industry to proactively detect, prevent, and manage the disease in the future.

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