Control of stripe rust on spring wheat cultivars with foliar fungicide in 2013

Authors: Chen, Xianming; Evans, Conrad; LIU, YUMEI - Washington State University

Submitted to: Plant Disease Management Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2014
Publication Date: 3/29/2014
Publication URL: http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2014/CF036.pdf
Citation: Chen, X., Evans, C.K., Liu, Y. 2014. Control of stripe rust on spring wheat cultivars with foliar fungicide in 2013. Plant Disease Management Reports. 8:CF034.

Interpretive Summary: To determine yield loss caused by stripe rust and fungicide benefit on individual spring wheat cultivars with various levels of resistance grown in the U.S. Pacific Northwest, a susceptible spring wheat variety (as a susceptible check) and 15 widely grown cultivars were tested in a field under natural infection of stripe rust near Pullman, WA using a randomized split-block design with four replications. Disease severity was assessed from each plot four times and grain test weight and yield were measured for each plot of no-spray and fungicide spray treatments of each cultivar. Area under disease progress curve (AUDPC) was calculated for each plot using the four sets of severity data . The effect of fungicide application on rAUDPC reduction and test weight and yield increases for each cultivar was determined by Fisher’s protected LSD test. The one time application protected the crops throughout the late growing season. The fungicide application significantly reduced rAUDPC on 10 cultivars. For test weight, only one cultivar and the suceptible check had significant increases. The fungicide application significantly increased grain yield on two of the commercially grown cultivars and the susceptible check from 14.23 to 15.09%. Based on the yield data, stripe rust caused yield losses from 0 to 20% with a mean of 8%, and fungicide application increased yield by 0 to 25% with a mean of 8%. The data of the study can be used to guide stripe rust management based on resistance and yield loss levels of individual cultivars.

Technical Abstract: To determine whether fungicide application is needed to control stripe rust on individual spring wheat cultivars with various levels of resistance grown in the U.S. Pacific Northwest, this study was conducted in a field under natural infection of stripe rust near Pullman, WA. Fertilizer Urea (46N-0K-0K) was applied at 100 lb/A at the time of cultivation on 18 Apr 13. Spring wheat genotype ‘Avocet S’ was used as a susceptible check and 15 spring wheat cultivars, including two new releases (Dayn and WA 8124), were selected based on their acreage planted in the State of Washington in 2011 and 2012. These genotype and cultivars were seeded in rows spaced 14 in. apart at 80 lb/A (99% germination rate) with a drill planter on 18 Apr 13. The plots were 4.4 ft in width and 15.5-17.7 ft in length. Herbicides (Huskie, 15 fl oz/A, Axial, 80 ml/A, and M-90, 140 ml/A) were applied on 15 May when wheat plants were at late seedling stage (Feeks 3). Fungicide Quilt 1.66 SE was sprayed at the rate of 14.0 fl oz/A mixed with surfactant M-90 at the rate of 1% v/v in 16 gallon water/A on 25 Jun when most plants were at flowering stage (Feeks 10.5) and stripe rust was only 1% severity on the susceptible check Avocet S. 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. A randomized split-block design was used with four replications. Disease severity (percentage of diseased foliage per whole plot) was assessed from each plot on 25 Jun at flowering stage, 13 Jul at milk stage, and 18 Jul at soft dough stage or on the fungicide application day and 18 and 23 days after application. Plots were harvested on 29 Aug when kernels had 3-5% kernel moisture and test weight of kernels was measured. Area under disease progress curve (AUDPC) was calculated for each plot using the three 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 reduction and test weight and yield increases for each cultivar was determined by Fisher’s protected LSD test. The development of stripe rust started relatively late and slowly due to the dry and hot weather conditions. The disease reached 10-15% severity on 13 Jul at milk stage and 70-95% on 18 Jul at soft dough stage in the plots of the susceptible check without fungicide application. The fungicide application in this field was at the right timing as the disease was just appearing. The one time application protected the crops throughout the late growing season as no obvious re-development of stripe rust in the sprayed plots up to the soft dough stage. The fungicide application significantly reduced rAUDPC for the susceptible check Avocet S and seven cultivars (Alpowa, Hank, Babe, Nick, Kelse, Jefferson, and Whit), but the reduction was not significant for the remaining eight cultivars as they have relatively high levels of resistance. The application provided excellent control of the disease as the reduction (93.24%) in the sprayed plots was almost complete compared to the no-sprayed plots of the susceptible check. For test weight, only the susceptible check and Alpowa had significant increases in sprayed plots compared to the no-sprayed plots. The fungicide application significantly increased grain yield for the susceptible check (15.09 bu/A, or 25.09%) and two commercially grown cultivars, Alpowa (14.47 bu/A, or 16.34%) and Hank (14.23 bu/A, or 18.94%). Based on the yield data of the no-sprayed and sprayed plots, stripe rust caused yield losses from -1.39 to 15.09 bu/A (-1.97 to 20.06%) with a mean of 6.28 bu/A (7.03%), and fungicide application increased yield by -1.94 to 25.09% with a mean of 8.01%. If only commercially grown cultivars are considered and weighted b