Testing fungicide Evito for control of stripe rust on spring wheat, 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. 2009. Testing fungicide Evito for control of stripe rust on spring wheat, 2008. Plant Disease Management Reports 3:CF040.

Interpretive Summary: Wheat stripe rust can cause severe damage on grain yield and quality. This study was conducted in 2008 to determine efficacy of fungicide Evito on control of stripe rust of spring wheat. Four treatments of Evito and three treatments of Quadris, Quilt, and Tilt, which have been registered for use on wheat to control stripe rust, were tested in a late-planted field expriment of randomized split-block design with 4 replications under natural infection of stripe rust. All treatments significantly reduced stripe rust severity 6 days after the second application in the field. Differences in stripe rust severity between the fungicide treatments and non-treated control remained significant thereafter. The treatment of Evito plus Tebuconazole provided the best control. All treatments significantly increased grain test weight by 0.8 to 1.3 lb/bu. Only the treatments of Evito at 2 fl oz/A and Tilt significantly increased grain yield. The late planting might affect efficacy of stripe rust control and increase of grain yield by the fungicide treatments. The results indicate that Evito can be used to control 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 ‘Lemhi’ spring wheat was seeded in rows spaced 14 in. apart at 60 lb/A with an experimental drill planter on 1 May 08. 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 30 May 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 application of Evito for the two-application treatment was done on 12 Jun at late tillering stage when there was no stripe rust in the plots. Sprays were applied when wind was 3.9 mph and temperature was about 68 oF. The one-time applications of Evito and Quadris, Tilt, and Quilt, which served as controls of registered fungicides for control of stripe rust, and the second application of Evito for the two-application treatments were done on 1 Jul when plants were at early flowering stage and stripe rust severity was about 1-10% in the plots. Sprays were applied when wind was 2.1 mph and temperature was about 72 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 77.5 to 86.7 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 2 Jul (heading), 7 Jul (flowering), 15 Jul (milk), 23 Jul (soft dough), and 31 Jul (dough) or 1, 6, 14, 22, and 30 days after the second fungicide spray, respectively. Plots were harvested on 1 Sep 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 was 6.5, 22.5, 67.5, 90.0, and 100.0% on 2 Jul, 7 Jul, 15 Jul, 23 Jul, and 31 Jul, respectively. All fungicide treatments significantly reduced stripe rust severity 6 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%), but varied significantly (1.0 – 71.2%) among the treatments. The treatment of Evito plus Tebuconazole provided the best control. Its efficacy was significantly better than those of the treatments of Evito at 2 fl oz/A and Quadris, but not significantly different from those of the other treatments. For unknown reasons, Quadris did not provide as excellent control as in the past. All treatments significantly increased grain test weight by 0.8 to 1.3 lb/bu. Only the treatments of Evito at 2 fl oz/A and Tilt significantly increased grain yield. Due to the late request, the plots were planted about 10 days later than the normal planting for the region, which might affect efficacy of stripe rust control and increase of grain yield by the fungicide treatments.