Evaluation of Pacific Northwest winter wheat cultivars for response to stripe rust and fungicide application in Pullman, WA, 2024

Authors: Chen, Xianming; Evans, Conrad; Messerlie, Peter

Submitted to: Plant Health Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/23/2025
Publication Date: 3/25/2025
Citation: Chen, X., Evans, C.K., Messerlie, P.M. 2025. Evaluation of Pacific Northwest winter wheat cultivars for response to stripe rust and fungicide application in Pullman, WA, 2024. Plant Health Progress. https://doi.org/10.1094/PHP-01-25-0023-PDMR.
DOI: https://doi.org/10.1094/PHP-01-25-0023-PDMR

Interpretive Summary: Stripe rust is a destructive disease of winter wheat, and the disease can be effectively controlled by planting resistant varieties and applying fungicides when needed. This study was conducted in a field near Pullman, WA under the natural infection of the stripe rust pathogen during the 2023-2024 crop season to determine yield losses by stripe rust and increases by fungicide for 23 major winter wheat varieties plus a susceptible check. The field was planted in the fall of 2023. For the spray plots, fungicide Quilt Xcel was applied at the early jointing stage and also the boot stage. Stripe rust severity was recorded four times from the early jointing to soft dough stage, and grain test weight and yield were measured for each plot at harvest. Relative area under the disease progress curve value (rAUDPC) was calculated using the four sets of severity data. The fungicide application significantly reduced stripe rust rAUDPC by 90.4% in the susceptible check, and rust reduction was also signifcant in 9 of the 23 commercially grown varieties. The fungicide application significantly increased grain test weight of the susceptible check and only one commercial variety. Significantly higher grain yield was observed in the susceptible check and 4 commercial varieties of the sprayed plots than the non-sprayed plots, whereas the remaining 19 varieties did not have significant diffences in yield, indicating adequate resistance. Based on the yield data, stripe rust caused yield loss of 61.2 bushels per acre (56.1%) for the susceptible check and 10.1 bushels per acre (7.5%) on average for the commercial varieties. The results are useful for growers to plant winter wheat varieties of high-yielding and high stripe rust resistance.

Technical Abstract: This study was conducted in a field near Pullman, WA under the natural infection of the stripe rust pathogen to evaluate the control of stripe rust with fungicide applications on major winter wheat cultivars grown in the U.S. Pacific Northwest and assess yield losses caused by the disease. Winter wheat genotype 'PS 279' was used as a susceptible check, and 23 cultivars were selected based on their high acreage planted in Washington state in 2023. The 24 entries were arranged in a randomized complete block design with a split-block constraint based on fungicide application, with four replications. They were seeded in rows spaced 14-in. apart at 60 lb/A (99% germination rate) with a drill planter on 30 Oct 23. The plots were 4.5-ft in width and 15.6 to 16.9-ft in length. Ammonium nitrogen fertilizer was applied at 100 lb/A at the time of planting. Herbicides (Huskie 15.0 fl oz/A + Axial Star 16.4 fl oz/A + M-90 10.4 fl oz/A) were applied on 15 May when wheat plants were at the early jointing stage (Feekes 5). On 15 May when stripe rust severity reached 1 to 5% in the PS 279 plots, Quilt Xcel 2.2SE was sprayed at the rate of 14.0 fl oz/A mixed with 0.25% v/v M-90 in 16-gallon water/A and sprayed again at the same rate on 30 May when plants were at the boot stage (Feekes 10) and stripe rust in the non-sprayed PS 279 plots was 25-40% severity. A 601C backpack sprayer was used with a CO2-pressurized spray boom at 18 psi having three operating 0.25-in. nozzles spaced 19-in. apart. Rust severity (percentage of stripe rust infected foliage per whole plot) was assessed from each plot on 14 May at the early jointing stage (Feekes 5), 29 May at the boot stage (Feekes 10), 12 Jun at the heading to flowering stage (Feekes 10.1-10.51), and 21 Jun at the milk to soft dough stage (Feekes 10-54-11.1) or 1 day before and 14, 28, and 37 days after the first time of the fungicide application. Plots were harvested on 2 Aug when kernels had 13 to 15% kernel moisture and test weight of kernels was measured. Area under the disease progress curve (AUDPC) was calculated for each plot using the four sets of severity data. Relative AUDPC (rAUDPC) was calculated as percent of the non-treated susceptible check. rAUDPC, test weight, and yield data were subjected to analysis of variance, and the effect of fungicide application on rAUDPC, test weight, and yield was determined in comparison with non-sprayed plots for each cultivar by Fisher's protected LSD test. Stripe rust was first observed on PS 279 plants in the nursery on 9 Apr 24 and reached 100% severity by 21 Jun at the milk to soft dough stage (Feekes 10.54-11.1) in the non-sprayed susceptible check plots. The two applications of Quilt Xcel at 14 fl oz/A reduced rAUDPC by 90.4% in the susceptible check (PS 279) plots. The fungicide applications also significantly reduced rAUDPC of nine commercial cultivars (UI Magic, Curiosity CL+, LCS Jet, Otto, Keldin, Mela CL+, LCS Helix, ARS-Crescent, and Castella), and the reduction ranged from 7.8 to 33.0%. The fungicide applications significantly protected grain test weight of the susceptible check (PS 279) by 5.2 lb/bu and UI Magic by 5.1 lb/bu. The fungicide applications made significant yield differences for the susceptible check (61.2 bu/A more in the sprayed plots) and four commercial cultivars (UI Magic, Curiosity CL+, LCS Jet, and Otto) with 24.5 to 52.6 bu/A more grain in the sprayed plots. The remaining 19 commercial cultivars (Keldin, Mela CL+, LCS Helix, Northwest Duet, ARS-Crescent, Stingray CL+, LCS Shine, Castella, Northwest Tandem, AP Iliad, Pritchett, LCS Blackjack, LCS Artdeco, Piranga CL+, SY Assure, M-Press, Resilience CL+, LCS Hulk, and SY Dayton) showed no significant yield differences between the no-spray and spray treatments. These data indicated that stripe rust caused yield losses of 61.2 bu/A (56.1%) on the susceptible check and 10.1 b