Submitted to: Plant Disease Management Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/30/2018
Publication Date: 3/12/2018
Citation: Chen, X., Evans, C.K., Sprott, J.A., Liu, Y. 2018. Evaluation of Pacific Northwest spring wheat cultivars to fungicide application for control of stripe rust in 2017. Plant Disease Management Reports. https://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2018/CF076.pdf.
Interpretive Summary: Most spring wheat cultivars grown in the U.S. Pacific Northwest (PNW) have resistance to stripe rust, but resistance in some cutlivars may not adequate under severe stripe rust epidemics. To evaluate spring wheat cultivars for their yield losses caused by stripe rust and responses to fungicide application, 23 spring wheat cultivars widely grown in the PNW plus a susceptible check were tested in a field near Pullman, WA in 2017. For the spray plots, fungicide, Quilt Xcel, was applied at the beginning of the rust season. Stripe rust severity was assessed for each plot four times and grain test weight and yield were measured. Relative area under disease progress curve (rAUDPC) was calculated using the severity data. The fungicide application significantly reduced stripe rust rAUDPC by more than 80% in the susceptible check and rust reduction was also signifcant in 16 cutlivars. The fungicide application significantly increased grain test weight of the susceptible check and four cultivars. Significant increase in grain yield was observed in the susceptible check and five cultivars, and the increases ranged from 13.5 to 41.4 bu/A (19.0-92.8%), whereas the 14 remaining cultivars had adequate resistance and did not have significant diffences in yield between sprayed and non-sprayed plots. Based on the yield data, stripe rust caused yield loss of 41.4 bu/A (48.1%) for the susceptible check and losses less than 21.0 bu/A (21.8%) for the cultivars at average of 6.2 bu/A (7.4%). The results are useful for control of stripe rust on spring wheat.
Technical Abstract: This study was conducted in a field near Pullman, WA to evaluate the control of stripe rust with fungicide applications on major spring wheat cultivars grown in the U.S. Pacific Northwest and assess their yield loss caused by the disease. Spring wheat genotype ‘Avocet S’ (AvS) was used as a susceptible check, and 23 spring wheat cultivars were selected based on their acreage planted in the state of Washington in 2016 or new releases. 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 15 May. The plots were 4.5 ft in width and 14.4 to16.6 ft in length. Urea (46N-0P-0K) was applied at 100 lb/A planting. Herbicides (Huskie 15.0 fl oz/A + Axial XL 16.4 fl oz/A + Starane Flex 13.5 fl oz/A + M-90 10.4 fl oz/A) were applied on 14 Jun when wheat plants were at the tillering stage (Feekes 3-4). Fungicide, Quilt 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 on 19 Jun when most plants were at the jointing stage (Feekes 3-4) and the susceptible check had no stripe rust. 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. Disease severity (percentage of diseased foliage per whole plot) was assessed from each plot on 19 Jun at Feekes 3-4, 5 Jul at Feekes 10.1, 19 Jul at Feekes 11.1, and 3 Aug at Feekes 11.3 or at 0, 16, 30, and 45 days after the fungicide application. Plots were harvested on 28 Aug when kernels had 3 to 5% 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 control. 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 AvS in late Jun when plants were at the early tillering stage (Feekes 5). The disease reached 90-100% severity in the non-sprayed susceptible check plots on 19 Jul at Feekes 11.1, 30 days after the fungicide application. The applications of Quilt Xcel 2.2SE at 14 fl oz/A controlled 83% of the stripe rust based on the susceptible check AvS. The fungicide application significantly reduced the rAUDPC for 17 cultivars in addition to the susceptible check, while the remaining 6 cultivars did not have significant stripe rust. The fungicide application significantly increased grain test weight of the susceptible check (AvS) and three commercially grown cultivars (WB-1035CL+, Kelse, and Expresso). The fungicide application significantly increased the grain yields of the susceptible check and five cultivars (WB6341, WB-1035CL+, Solano, Babe, and Alpowa), and the significant increases ranged from 13.5 to 41.4 bu/A (19.0-92.8%), whereas the remaining 18 cultivars (JD, Melba, Kelse, SY 605CL, Buck Pronto, Alum, WB Hartline, SY Steelhead, Dayn, Expresso, Seahawk, Louise, Whit, Chet, Glee, WB6121, WB9518, and Diva) did not have significant yield increases by the fungicide applications, indicating that these cultivars have adequate levels of resistance against stripe rust under the severe level of epidemic. These data also indicated that stripe rust caused yield loss of 41.37 bu/A (48.13%) on the susceptible check and 7.4% on average across the commercially grown cultivars. Under the severe stripe rust epidemic in 2017, about 22% of the spring wheat cultivars needed application of effective fungicide, such as Quilt Xcel, to protect yield.