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Title: Control of stripe rust on winter wheat cultivars with foliar fungicide in 2013

item Chen, Xianming
item Evans, Conrad
item LIU, Y. - 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:
Citation: Chen, X., Evans, C.K., Liu, Y.M. 2014. Control of stripe rust on winter wheat cultivars with foliar fungicide in 2013. Plant Disease Management Reports. 8:CF35.

Interpretive Summary: A total of 19 foliar fungicide treatments were tested for their efficacy in control of stripe rust on winter wheat during the 2012-2013 crop season. The experimental field near Pullman, WA was planted with a susceptible winter wheat variety on October 30, 2012. A randomized complete block design experiment with four replications was used including a non-treated check treatment. Fungicides were applied on two dates and crop growth stages depending upon the treatments. Disease severity was assessed from each plot five times during the disease season under the natural infection of stripe rust. Area under the disease progress curve (AUDPC) was calculated for each plot using the five sets of severity data. Relative AUDPC was calculated as percentage of the non-treated control. Grain yield and test weight were measured. Rust severity, relative AUDPC, test weight, and yield data were subjected to analysis of variance and means were compared to determine the difference among the treatments. Stripe rust started early, but developed slowly due to the hot and dry weather conditions, and eventually reached 100% severity at dough stage and caused more than 40% yield loss in the non-treated control plots. All fungicide treatments, but one, significantly reduced rust AUDPC and increased test weight. Except four treatments, all treatments increased grain yield compared to the non-treated control. Some of the treatments provided better control than others. Yield increases of the fungicide applications ranged from 1% to 73%. Some of the new formulations could be registered for control of stripe rust.

Technical Abstract: The study was conducted in a field with Palouse silt loam under natural infection of stripe rust near Pullman, WA. Fertilizer (Osmocota 14-14-14) was applied at 60 lb/A at the time of cultivation on 29 Oct 2012. Stripe rust susceptible ‘PS 279’ winter wheat was seeded in rows spaced 14 in. apart at 60 lb/A (99% germination rate) with a drill planter on 30 Oct 2012. Nitrogen fertilizer (46-0-0) and herbicides (Huskie, 15 fl oz/A, Axial, 80 ml/A, and M-90, 140 ml/A) were applied on 7 May 2013 when wheat plants were at the early jointing stage. Before the first fungicide application, the field was divided into individual plots of 4.4 ft (4 rows) in width and 15.1 to 16.8 ft in length by eliminating plants between plots with a rototiller. Fungicides were applied in 16 gal water/A on different dates and stages depending upon the treatment. The first fungicide application timing at jointing stage (Feekes 5) was made on 20 May when stripe rust was 0 to 5% severity in the field. The second application was done at the boot stage (Feekes 10) on 11 Jun when stripe rust in the plots without first fungicide application reached 8 to 35% 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. A randomized block design was used with four replications. Disease severity (percentage of diseased foliage per whole plot) was assessed from each plot on 20 May, 10 Jun, 17 Jun (data not presented), 25 Jun, and 3 Jul or on the day of fungicide application and 21, 28, 36, and 44 days after the first fungicide application timing, respectively. Plots were harvested on 5 Aug when kernels had 3 to 5% kernel moisture and test weight of kernels was measured. Area under 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 control. Rust severity, rAUDPC, test weight, and yield data were subjected to analysis of variance and means were separated by Fisher’s protected LSD test. The first fungicide was applied as stripe rust began to develop (Feekes 5) and the second application as the disease reached 8 to 35% severity (Feekes 10) in the plots without the first application. Stripe rust reached 100% severity in the nontreated check plots approximately 44 days after the first application, slower than in the past several years as the weather was hot and dry during the late growing season. All fungicide treatments significantly reduced rust severity compared to the nontreated at the milk stage. The rAUDPC values of all treatments were significantly less than the nontreated, except the treatment of Topguard alone at Feekes 10. Among all treatments, the treatments of Aproach at Feekes 5 followed by Aproach Prima at Feekes 10 provided the best disease control, but the treatments of Topguard 5 fl oz/A at Feekes 5 followed by Feekes 10, A18126 4.76 ozwtpr/A at Feekes 10, and A15457 4.1 fl oz/A plus Tilt + Quadris at Feekes 10 had similar control. Among the single fungicide treatments with one application at Feekes 10, A18126 2.86 ozwtpr/A, A18126 4.67 ozwtpr/A, A18993 9 fl oz/A, Aproach 6.0 fl oz/A, Aproach Prima at 3.4 fl oz/A, 5.0 fl oz/A, and 6.8 fl oz/A, Custodia 8.6 fl oz/A, and Quilt Xcel 10.5 fl oz/A provided similar levels of stripe rust control. All treatments, except Topguard 14 fl/A at Feekes 10, significantly increased test weight compared to the nontreated. The treatment of A15457 4.1 fl oz/A + Tilt 4.0 fl oz/A + Quadris 6 fl oz/A at Feekes 10 produced the greatest test weight, and the test weights of eight other treatments were not significantly different from one another. Except treatments made at Feekes 10 with Topguard 14 fl oz/A, Aproach 6.0 fl oz/A, Aproach Prima 5.0 fl oz/A, and Bumper 4 fl oz/A, all other treatments significantly increased yield