Control of stripe rust of winter wheat with foliar fungicides

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

Submitted to: Plant Disease Management Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/22/2013
Publication Date: 3/11/2013
Citation: Chen, X., Evans, C.K., Garner, J.P., Liu, Y. 2013. Control of stripe rust of winter wheat with foliar fungicides. Plant Disease Management Reports. 7:CF032.

Interpretive Summary: A total of 17 foliar fungicide treatments were tested for their efficacy in control of stripe rust on winter wheat during the 2011-2012 crop season. The experimental field near Pullman, WA was planted with a susceptible winter wheat cultivar, PS 279, on October 25, 2011. A randomized complete block design experiment with four replications was used including a non-treated check treatment. Fungicides were applied on three different 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 four 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 reached 100% severity at milk stage and caused more than 53% yield loss in the non-treated control plots. All fungicide treatments significantly reduced rust severity, increased test weight, and 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 47% to 111%. Some of the new formulations may 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 25 Oct 11. 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 26 Oct 11. Huskie, 15 fl oz/A, plus Axial, 80 ml/A, and M-90, 140 ml/A, were applied on 30 May when wheat plants were at early jointing stage. Before the first fungicide application the field was divided into individual plots of 4.4 ft (4 rows) in width and 14.8-17.0 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 was done on 3 Jun when stripe rust was 1-5% severity in the field. The second application was done at boot stage on 15 Jun when stripe rust in the non-treated plots reached 20-30% severity. The third was done at heading stage on 25 Jun when stripe rust in the non-treated plots reached 90% 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 3 Jun, 18 Jun, 25 Jun, 6 Jul (data not shown), and 13 Jul or on the day of fungicide application and 15, 22, 33, and 40 days after the first fungicide application timing, respectively. Plots were harvested on 16 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 five sets of severity data. Relative AUDPC was calculated as percent of the non-treated control. Rust severity, relative AUDPC, test weight, and yield data were subjected to analysis of variance and means were separated by Fisher’s protected LSD test.