Evaluation of Pacific Northwest winter wheat cultivars to fungicide application for control of stripe rust in 2023

Authors: Chen, Xianming; Evans, Conrad; QIN, RUIJUN - Oregon State University

Submitted to: Plant Disease Management Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/2024
Publication Date: 3/2/2024
Citation: Chen, X., Evans, C.K., Qin, R. 2024. Evaluation of Pacific Northwest winter wheat cultivars to fungicide application for control of stripe rust in 2023. Plant Disease Management Reports. 18. Article CF068.

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. This study was conducted in a field near Pullman, WA during the 2022-2023 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 2022 and inoculated with wheat stripe rust spores in the spring 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 five 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 five sets of severity data. The fungicide application significantly reduced stripe rust rAUDPC by 98.1% in the susceptible check, and rust reduction was also signifcant in 11 of the 23 commercially grown varieties. The fungicide application significantly increased grain test weight of the susceptible check and three commercial varieties. Significantly higher grain yield was observed in the susceptible check and 6 commercial varieties of the sprayed plots than the non-sprayed plots, whereas the remaining 17 varieties did not have significant diffences in yield, indicating adequate resistance. Based on the yield data, stripe rust caused yield loss of 32.6 bushels per acre (32.6%) for the susceptible check and 6.7 bushels per acre (5.0%) on average for the commercial varieties. The results are useful for managing stripe rust based on individual winter wheat varieties.

Technical Abstract: This study was conducted in a field near Pullman, WA 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 loss 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 the state of Washington in 2022. The 24 entries were arranged in a randomized split block design 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 19 Oct 22. 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. The field was inoculated on 10 Apr (Feekes 2-3) with urediniospores of the wheat stripe rust pathogen collected from the same farm in 2022. Herbicides (Huskie 15.0 fl oz/A + Axial XL 16.4 fl oz/A + M-90 10.4 fl oz/A) were applied on 12 May when wheat plants were at the early jointing stage (Feekes 4-5). On 19 May when most plants were at the early jointing stage (Feekes 5) and stripe rust just appeared (0.1% severity in 4 of the 192 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 2-5% severity. A 601C backpack sprayer was used with a CO2-pressurized spray boom at 18 psi having three operating ¼ in. nozzles spaced 19-in. apart. Rust severity (percentage of stripe rust infected foliage per whole plot) was assessed from each plot on 18 May at the early jointing stage (Feekes 5), 31 May at the boot stage (Feekes 10), 12 Jun at the flowering stage (Feekes 10.51), 20 Jun at the milk stage (Feekes 10.54), and 28 Jun at the soft dough stage (Feekes 11.1) or 1 day before and 11, 24, 32, and 40 days after the first time of the fungicide application. Plots were harvested on 3 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 five 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 18 May 23 and reached 100% severity by 28 Jun at the soft dough stage (Feekes 11.1) in the non-sprayed susceptible check plots. The two applications of Quilt Xcel at 14 fl oz/A reduced rAUDPC by 98.1% in the susceptible check (PS 279) plots. The fungicide applications also significantly reduced rAUDPC of twelve commercial cultivars (UI Magic, LCS Jet, Curiosity CL+, Otto, Mela CL+, Stingray CL+, ARS-Crescent, Piranha, Keldin, WB4303, Pritchett, and LCS Artdeco), and the reduction ranged from 3.3 to 56.3%. The fungicide applications significantly protected grain test weight of the susceptible check (PS 279) by 5.4 lb/bu and three commercial cultivars (UI Magic, Curiosity CL+, and Stingray CL+) by 1.3 to 1.6 lb/bu. The fungicide applications made significant yield differences for the susceptible check (32.6 bu/A more in the sprayed plots) and six commercial cultivars (UI Magic, LCS Jet, Curiosity CL+, Otto, Mela CL+, and Stingray Cl+) with 12.0 to 27.0 bu/A more grain in the sprayed plots. The remaining 17 commercial cultivars (LCS Hulk, ARS-Crescent, Sockeye CL+, Piranga CL+, Kelding, WB4303, SY Assure, Pritchett, LCS Shine, Northwest Tandem, AP Exceed, Northwest Duet, LCS Jefe, LCS Artdeco, Resilience CL+, M