Control of stripe rust of winter wheat with foliar fungicides, 2008

Authors: Chen, Xianming; Wood, David

Submitted to: Plant Disease Management Reports
Publication Type: Research Notes
Publication Acceptance Date: 5/1/2009
Publication Date: 6/30/2009
Citation: Chen, X., Wood, D.A. Control of stripe rust of winter wheat with foliar fungicides, 2008. Plant Disease Management Reports 3:CF038.

Interpretive Summary: Wheat stripe rust can cause severe damage on grain yield and quality. This study was conducted in 2008 to determine efficacy of a couple of new fungicide formulations on control of stripe rust of winter wheat. A total of 11 treatments of 5 fungicides, including new formulations Topguard and BAS 556, were tested in a field expriment of randomized split-block design with 4 replications under natural infection of stripe rust. All fungicide treatments significantly reduced stripe rust severity 7 days after the application in the field. Differences in stripe rust severity between the fungicide treatments and non-treated control remained significant thereafter. Treatments with two applications of Topguard at 10 fl oz/A and one application of Headline, BAS 556 at 9 fl oz/A, Quilt at 14 fl oz/A and Stratego at 10 fl oz/A significantly increased grain test weight of 'PS 279' wheat and none of the treatments significantly increased grain test weight of 'Hatton' wheat. All treatments significantly increased grain yield on PS 279 ranging from 31.3 to 42.4%, but the increases (from -0.3 to 5.8%) on Hatton were not significant, compared to the non-treated control. The treatments of Topguard and BAS 556 reduced stripe rust and increased yield as equally well as other fungicides that have been registered for use on wheat to control stripe rust. The results should be useful for registering these two fungicides for control of wheat stripe rust.

Technical Abstract: The study was conducted in a field with Palous silt loam under natural infection of stripe rust near Pullman, WA. Urea (46-0-0) was applied at 60 lb/A at the time of cultivation. Susceptible wheat cultivars ‘Hatton’ and ‘PS 279’ were seeded in rows spaced 14 in. apart at 60 lb/A with an experimental drill planter on 16 Oct 07. Harmony Extra 0.33 oz plus Buctril 0.75 pt/A with Agridex crop oil concentrate (COC) at 1% of spray volume was applied on 13 May 08 when wheat plants were at tillering stage. Fungicides were applied in 16 gal water/A on different dates and stages depending upon the treatments. The first applications of Topguard for the two-application treatments were done on 24 May at late jointing stage when there was no stripe rust in the plots. Sprays were applied when wind was 4.3 mph and temperature was about 60 oF. The one-time applications of Topguard, Headline, BAS 556, Quilt, and Stratego and second application of Topguard were done on 12 Jun when plants were at boot stage. Sprays were applied when wind was 3.1 mph and temperature was about 66 oF. A 601C backpack sprayer from R & D Sprayers Inc. was used with a C3470 regulator and a 2.5 lb CO2 cylinder. The spray boom had four nozzles 19 in apart, but three were used because of the width of the plots. The spray pressure was 18 psi. A randomized block design was used with four replications for each treatment. Plots, ranging from 82.5 to 86.0 sq ft., were individually measured at the time of harvest and individual plots areas were used to calculate yields. Stripe rust severity (percentage of diseased foliage) was assessed in each plot on 12 Jun just before the second fungicide application and 19 Jun (early heading), 26 Jun (early flowering), 3 Jul (early milk), 10 Jul (soft dough), and 16 Jul (dough) or 7, 14, 21, 28, and 34 days after the second fungicide spray, respectively. Plots were harvested on 6 Aug when kernels were naturally dry, and test weight of kernels was measured for each plot. Area under disease progress curve (AUDPC) was calculated for each plot using the six 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. Mean stripe rust severity in non-treated control plots of Hatton was 1.0, 1.3, 13.8, 45.0, 70.0, and 85.0% on 12 Jun, 19 Jun, 26 Jun, 3 Jul, 10 Jul, and 16 Jul, respectively; and that of PS 279 was 1.0, 18.0, 37.5, 77.5, 97.5, and 100.0% on these dates, respectively. All fungicide treatments significantly reduced stripe rust severity 7 days after the second application in the field. Differences in stripe rust severity between the fungicide treatments and non-treated control remained significant thereafter. Relative AUDPC values of all fungicide treatments were significantly lower than the non-treated control (100%), and were not significantly different from each other due to the relatively short disease season and low disease pressure compared with previous years. Treatments with two applications of Topguard at 10 fl oz/A and one application of Headline, BAS 556 at 9 fl oz/A, Quilt at 14 fl oz/A and Stratego at 10 fl oz/A significantly increased grain test weight of PS 279 and none of the treatments significantly increased grain test weight of Hatton. All treatments significantly increased grain yield on PS 279 ranging from 31.3 to 42.4%, but the increases (from -0.3 to 5.8%) on Hatton were not significant, compared to the non-treated control.