P-106 - Evaluation of fungicide timing and efficacy for the management of oat crown rust in North Dakota

Oat crown rust, caused by the pathogen Puccinia coronata f. sp. avenae, is the most destructive disease in oat production in North Dakota. Due to the abilities of the pathogen to overwinter in ND and to overcome host resistance, fungicides are an important management tool often used by growers to manage disease. In an effort to update management tools available to growers, nine fungicide trials evaluating efficacy and timing were established between 2016 to 2024 at two locations in North Dakota. Trials were conducted in a randomized complete block design with four replicates. All trials were sown with a susceptible oat variety and relied on natural disease pressure. In 2016 and 2017, treatments included a non-treated control (NTC), Headline® (pyraclostrobin), Priaxor® (fluxapyroxad + pyraclostrobin), Quadris® (azoxystrobin), and Tilt® (propiconazole). All fungicides were applied at Feekes 9 (flag leaf; FGS 9). In 2021 to 2024, Headline and Quadris were replaced with Sphaerex® (metconazole + prothioconazole) applied at Feekes 10.5 (fully emerged head; FGS 10.5) and Quilt Xcel® (propiconazole + azoxystrobin) applied at FGS 9. Moderate to high levels of crown rust developed in six of the nine experiments. Results suggested that all fungicide treatments reduced crown rust severity and protected yield, regardless of the product or application timing. This suggests that a fungicide application between FGS 9 and FGS 10.5 is effective for crown rust management. Information from this trial has been used to support crown rust fungicide decisions in the Northern Great Plains.