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Assessing the Curative and Residual Control of Wheat Powdery Mildew with Fungicides

Nathan Kleczewski: University of Illinois

<div>Fungicide efficacy trials in wheat are often conducted in the field, and researchers often cannot separate direct curative or residual activity from the impact of a fungicide on inoculum buildup, arrival, and spread. To address this, a set of greenhouse experiments were conducted on the fungicides Prosaro, Caramba, Trivapro, Priaxor, and Stratego YLD using a local isolate of powdery mildew (<span><em>Blumeria graminis</em> (DC.) Speer f. sp. <em>Tritici)</em></span>. Curative activity was assessed by inoculating 14-day-old pots of Roane wheat 5 days prior to fungicide application. Residual activity was assessed by inoculating plants at 42 days after fungicide application. Disease severity was determined 10 days after inoculation. Each fungicide by inoculation treatment was replicated 6 times per experiment and each experiment was replicated twice. In 5-day curative trials Trivapro reduced disease severity by 99%. Stratego YLD, Prosaro, and Trivapro reduced disease by 71, 63 and 59% in 42-day residual experiments, respectively. In field trials, Caramba is considered to have superior curative control. Similarly, Stratego YLD often is not considered to provide excellent residual control for fungal diseases, whereas Trivapro is marketed as having superior residual control compared to other fungicides. These results indicate that fungicide performance in the field may be due to other factors that may influence perceived curative and residual product performance.</div>