Control of stripe rust of winter wheat with various foliar fungicides, 2015

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

Submitted to: Plant Disease Management Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/24/2016
Publication Date: 3/7/2016
Citation: Chen, X., Evans, C.K., Liu, Y. 2016. Control of stripe rust of winter wheat with various foliar fungicides, 2015. Plant Disease Management Reports. 10:CF:022.

Interpretive Summary: Stripe rust of wheat is best controlled by developing and growing resistant cultivars, but resistant cultivars become susceptible or the resistance is not adequate, fungicide application is needed to reduce yield loss. In this study, 19 foliar fungicide treatments were tested for efficacy in control of stripe rust during the 2014-2015 crop season using a randomized complete block design with four replications for each treatment plus a non-treated chech. The experimental field near Pullman, WA was planted with a susceptible winter wheat variety 'PS 279' on October 16, 2013. Fungicides were applied at early jointing stage and/or boot stage depending upon the treatments. Disease severity was assessed five times during the stripe rust development of natural infection. 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 check. 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 differences among the treatments. Stripe rust reached 100% severity at milk stage, allowing adequate evaluation of fungicide efficacy. All fungicide treatments significantly reduced rust AUDPC. All treatments significantly increased test weight, and 17 of them significantly increased grain yield compared to the non-treated check, and the significant yield increases ranged from 20.69 to 34.31%. The results can be used for registering new fungicides and for control of stripe rust.

Technical Abstract: The study was conducted in a field with Palouse silt loam soil near Pullman, WA. 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 16 Oct 2014. Nitrogen fertilizer (46-0-0) was applied at the rate of 100 lb/A at the time of planting and also applied at the rate of 100 lb/A on May 1, 2015 when plants were at Feekes 4-5. Before the first fungicide application, the field was divided into individual plots of 4.5 ft (4 rows) in width and 16.0 to 17.1 ft in length by eliminating plants between plots by spraying herbicide (Allecto, 24 fl oz/A mixed with surfactant M-90, 14 fl oz/A) on 4 May. Herbicides (Huskie, 15 fl oz/A, Axial XL, 16.4 fl oz/A, and M-90, 10.4 fl oz/A) were applied to the entire field to control weeds on 8 May 2015 when wheat plants were at the early jointing stage (Feekes 5). Fungicides were applied in 16 gal water/A on different dates and stages depending upon the treatment. The first fungicide application timing at the early jointing stage (Feekes 5) was made on 6 May when stripe rust was 0 to 1% severity in the field. The second application was done at the boot stage (Feekes 10) on 20 May when stripe rust in the plots without first fungicide application reached 1 to 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. A randomized block design was used with four replications. Disease severity (percentage of diseased foliage per whole plot) was assessed from each plot on 6 May (data not presented), 20 May, 15 Jun, 22 Jun, and 30 Jun or 0, 14, 40, 47, and 55 days after the first fungicide application timing, respectively. Plots were harvested on 4 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. Stripe rust from natural infection started developing in the plots in early May when plants were at the early jointing stage (Feekes 5) and reached 80% and 100% severity at the flowering and milk stages, respectively in the nontreated check plots. All fungicide treatments significantly reduced rust severity compared to the nontreated at the flowering, milk, and dough stages, except the treatments of Tilt 2.0 fl oz/A and Tilt 4.0 fl oz/A applied at Feekes 5 recorded at the milk and/or dough stages. The rAUDPC values of all treatments were significantly less than the nontreated. All treatments provided similar control of stripe rust except Tilt 2.0 fl oz/A and Tilt 4.0 fl oz/A applied at Feekes 5 and Quadris 8.0 fl oz/A applied at Feekes 10. All treatments significantly increased test weight compared to the nontreated. The treatments of HM 0812 10.5 fl oz/A applied at Feekes 10, Tilt 2.0 fl oz/A applied at Feekes 5 followed by Quilt Xcel 10.5 fl oz/A applied at Feekes 10, Tilt 4.0 fl oz/A applied at Feekes 5 followed by Quilt Xcel 10.5 oz/A applied at Feekes 10, and Tilt 4.0 fl oz/A applied at Feekes 10 produced the highest test weight. Except the treatments of Tilt 2.0 fl oz/A and Tilt 4.0 fl oz/A applied at Feekes 5, all treatments significantly increased yield compared with the nontreated, and the significant increases ranged from 20.69% by the treatment of A15457K 4.0 fl oz/A + Quilt Xcel 10.5 fl oz/A applied at Feekes 5 followed by A15457K 4.0 fl oz/A + Quilt Xcel 10.5 fl oz/A applied at Feekes 10 to 34.31% by the treatment of HM 0812 14.0 fl oz/A applied at Feekes 10. Except these two treatments, the yields of the other treatments with significant yield increases com