Control of stripe rust of spring wheat with foliar fungicides, 2010

Authors: Chen, Xianming; Wood, David

Submitted to: Plant Disease Management Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/16/2010
Publication Date: 4/1/2011
Citation: Chen, X., Wood, D.A. 2011. Control of stripe rust of spring wheat with foliar fungicides, 2010. Plant Disease Management Reports. 5:CF003.

Interpretive Summary: A total of 31 fungicide treatments plus a non-treated control were tested for their efficacy in control of stripe rust on spring wheat during the 2010 crop season. The experimental field near Pullman, WA was planted with a susceptible spring wheat cultivar, Lemhi, on April 30, 2010. Fungicides were applied on different dates and stages depending upon the treatments. Disease severity was assessed from each plot three 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 three sets of severity data. Relative AUDPC was calculated as percent of the non-treated control. Grain yield and 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. All fungicide treatments significantly prevented rust development by 6 Jul and rust severity differences of 27 treatments from the non-treated control remained significant 27 days after the second application. Relative AUDPC values of all treatments were significantly less than the non-treated control, and were significantly different among some of the treatments. Six treatments provided the best control. Fifteen treatments significantly increased grain test weight. Except two treatments, all fungicide treatments significantly increased grain yield by 23.1% to 66.9%. The information should be useful for control of stripe rust on spring wheat.

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 (99% germination rate) with a drill planter on 30 Apr 10. 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 2 Jun 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 16.0-17.9 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 treatments. The first fungicide application timing at late jointing was done on 18 Jun when stripe rust was just appearing (1% severity) and the second timing at early boot on 22 Jun when stripe rust reached 5% severity. A 601C backpack sprayer was used with a CO2 pressurized spray boom at 18 psi having three operating nozzles spaced 19 in apart. A randomized block design was used with four replications. Disease severity (percentage of diseased foliage on whole plot) was assessed from each plot on 6 Jul, 19 Jul, and 26 Jul or 14, 27, and 34 days after the second fungicide application timing, respectively. Plots were harvested on 30 Aug when kernels were naturally dry, and test weight of kernels was measured. Area under disease progress curve (AUDPC) was calculated for each plot using the four 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. All fungicide treatments significantly prevented rust development by 6 Jul compared with the non-treated control. Differences in stripe rust severity between the fungicide and non-treated control treatments remained significant 27 days after the second fungicide application timing for all treatments except the treatments of Topguard at 7 and 10 fl oz/A and BAS 70302F at 2.47 and 3.00 fl oz/A at late jointing stage. Relative AUDPC values of all treatments were significantly less than the non-treated control, and were significantly different among some of the treatments. The treatments of Quilt 1.66 SC at 14 fl oz/A, Quilt Xcel 2.20 SC at 10.5 fl oz/A, Tilt 3.60 EC at 4.0 fl oz/A, Prosaro, Muscle, and Headline at 3.0 plus Tilt (Pumper) 432 EC at 4.0 fl oz/A were in the best ranking group for controlling stripe rust. Of the 31 fungicide treatments, 15 significantly increased grain test weight. Except for the treatments of BAS 7004F at 4.57 fl oz/A and BAS 70302F at 2.47 fl oz/A sprayed at late jointing, all fungicide treatments significantly increased grain yield by 23.1% from 3.0 fl oz/A Headline 250 EC at late jointing stage to 66.9% from Muscle.