To determine the effects of fungicide application on control of stripe rust on individual winter wheat cultivars with various levels of resistance grown in the U.S. Pacific Northwest, this study was conducted in a field near Pullman, WA. Fertilizer (100N-20K-25S) was applied at 80 lb/A at the time of cultivation on 10 Oct 13. Winter wheat genotype 'PS 279' was used as a susceptible check and 23 cultivars were selected based on their acreage planted in the State of Washington in 2013 or new releases.These genotype and cultivars were seeded in rows spaced 14 in. apart at 60 lb/A (99% germination rate) with a drill planter on 10 Oct 13. The plots were 4.5 ft in width and 14.3 to16.3 ft in length. Because a low level of stripe rust was predicted for the 2014 season, the field was inoculated with a mixture of locally predominant races PSTv-14 and PSTv-37 of Puccinia striiformis f. sp. tritici on 16 Apr 14 at late tillering stage (Feekes 3). Urea (46N-0P-0K) at 125 lb/A was applied on 28 Apr 14 at the early stage (Feekes 4) and herbicide (Allecto, 24 fl oz/A mixed with surfactant M-90, 14 fl oz/A) was applied on 12 May when wheat plants were at the early jointing stage (Feekes 5). Fungicide Quilt 1.66 SE was sprayed at the rate of 14.0 fl oz/A mixed with M-90 at the rate of 1% v/v in 16 gallon water/A on 29 May when most plants at boot-heading stage and stripe rust reached 10% severity on the susceptible check PS 279. A 601C backpack sprayer was used with a CO2-pressurized spray boom at 18 psi havingthree operating % in. nozzles spaced 19 in. apart. A randomized complete block design was employed with a split block based on spray or not spray and with four replications. Disease severity (percentage of diseased foliage per whole plot) was assessed from each plot on 27 May at boot stage, 10 Jun at flowering stage, and 24 Jun at soft dough stage or two days before the fungicide application and 12 and 26 days after application. Plots were harvested on 6 Aug when kernels had 3 to 5% kernel moisture andtest weight of kernels was measured. Area under the 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, andyield 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 LSDtest.
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