P-416 - Occurrence of stripe rusts in North Dakota, race characterization, and impacts on wheat yield

The stripe rust caused by Puccinia striiformis f. sp. tritici was detected in multiple locations across North Dakota in 2024, with significant disease severity impacting wheat yield. A disease survey was conducted across major wheat production regions in North Dakota in July 2024 to assess stripe rust on wheat and collect pathogen isolates for race characterization. Disease severity and infection types were evaluated in wheat variety performance trials conducted by NDSU at Hettinger, Dickinson, Williston, Casselton, and Langdon. The results showed that the coefficient of infection (COI), converted from disease severity data, ranged from 0 to 30.4 across locations. COI varied significantly across the state, with Dickinson (30.4) and Hettinger (22.1) exhibiting the highest COI values, while other locations had lower infection levels (0–9.4). The significant differences in COI between locations suggest the influence of environmental conditions at each site as well as the seasonal migration of urediniospores from the southern and western United States into North Dakota. Our analysis also indicated a significant impact of stripe rust on straw strength, test weight, and yield. Additionally, we collected 18 isolates, which are currently being characterized for race identification. The results of the race characterization will be presented.