CONTROL OF STRIPE RUST OF WINTER WHEAT WITH FOLIAR FUNGICIDES, 2005

Authors: Chen, Xianming; Wood, David

Submitted to: Fungicide and Nematocide Tests
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2006
Publication Date: 4/20/2006
Citation: Chen, X., Wood, D.A. 2006. Control of stripe rust of winter wheat with foliar fungicides, 2005. F&N Tests 61:CF023.

Interpretive Summary: The study was conducted in a field under natural infection of stripe rust near Pullman, WA. Fungicides were applied at late jointing stage when stripe rust severity was at 20-40% on leaves. Stripe rust severity (percentage of diseased foliage) was assessed in each plot just before fungicide application. Plots were harvested on 15 Aug. Stripe rust severity in non-treated control plots was 32.5, 80, 95, 100, and 100% on 21 May, 31 May, 6 Jun, 15 Jun, and 23 Jun, respectively. All fungicide treatments effectively reduced stripe rust severity 10 days after application. By 25 days after fungicide application, treatments with Absolute, Sparta, Quilt, Tilt and Folicur showed better control of stripe rust, than Stratego. Rust severity increased to 40, 50, and 62.5% in the plots treated with Flutriafol, Headline, and Quadris, respectively, indicating that these treatments had become less effective 25 days after application. By 33 days after application, stripe rust severity in plots treated with Tilt, Headline, Flutriafol, Stratego, and Quadris were not significantly different from the non-treated control plot. The treatments with Absolute and two-applications of Quilt remained effective, while plots treated with Sparta, Folicur, and one application of Quilt showed a significant increase of rust severity. Only the treatments with Absolute, Sparta, or two applications of Quilt significantly increased test weight. All fungicide treatments significantly increased yield by 145 to 286% of the yield of the non-treated control. Stripe rust damage was much higher and the yield response to fungicide treatments was much greater in 2005 compared to previous field trials (2000-2004), because of the long duration of the epidemic season in 2005.

Technical Abstract: The study was conducted in a field under natural infection of stripe rust near Pullman, WA. Fungicides were applied 21 May at late jointing stage when stripe rust severity was at 20-40% on leaves. In the treatment with two sprays of Quilt plus COC, the first spray was applied on 21 May at late jointing and a second spray was applied on 6 Jun at boot stage. A randomized block design was used with four replications for each treatment. Stripe rust severity (percentage of diseased foliage) was assessed in each plot on 21 May just before fungicide application; 31 May or 10 days after fungicide application; 6 Jun or 16 days after fungicide application at boot stage; 15 Jun or 25 days after fungicide application at early heading stage; and 23 Jun or 33 days after fungicide application at late flowering stage. Plots were harvested on 15 Aug. Stripe rust severity in non-treated control plots was 32.5, 80, 95, 100, and 100% on 21 May, 31 May, 6 Jun, 15 Jun, and 23 Jun, respectively. All fungicide treatments effectively reduced stripe rust severity 10 days after application. Except Quadris, all treatments were effective in maintaining disease control up to 16 days after fungicide application. By 25 days after fungicide application, treatments with Absolute, Sparta, Quilt, Tilt and Folicur showed better control of stripe rust, than Stratego. Rust severity increased to 40, 50, and 62.5% in the plots treated with Flutriafol, Headline, and Quadris, respectively, indicating that these treatments had become less effective before 15 Jun or 25 days after application. By 33 days after application, stripe rust severity in plots treated with Tilt, Headline, Flutriafol, Stratego, and Quadris were not significantly different from the non-treated control plot. The treatments with Absolute and two-applications of Quilt remained effective, while plots treated with Sparta, Folicur, and one application of Quilt showed a significant increase of rust severity. Only the treatments with Absolute, Sparta, or two applications of Quilt significantly increased test weight. All fungicide treatments significantly increased yield by 145 to 286% of the yield of the non-treated control. Stripe rust damage was much higher and the yield response to fungicide treatments was much greater in 2005 compared to previous field trials (2000-2004), because of the long duration of the epidemic season in 2005.