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 spring wheat with foliar fungicide. Plant Disease Management Reports. 7:CF031. Interpretive Summary: A total of 29 foliar fungicide treatments were tested for their efficacy in control of stripe rust on spring wheat during the 2012 crop season. The experimental field near Pullman, WA was planted with a susceptible winter wheat cultivar, Lemhi, on April 19, 2012. A randomized complete block design experiment with four replications was used including a non-treated check treatment. Fungicides were applied on two 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 dough stage and caused more than 36% yield loss in the non-treated control plots. All fungicide treatments significantly reduced rust severity and increased test weight; and all treatments except one significantly 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 55%. Some of the new formulations may be registered for control of stripe rust.
Technical Abstract: The experiment 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 19 Apr. Susceptible ‘Lemhi’ spring wheat was seeded in rows spaced 14 in. apart at 60 lb/A (99% germination rate) with a drill planter on 19 Apr. Huskie 15 fl oz plus Axial 80 ml and M-90 140 ml/A was applied on 3 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 15.6-18.1 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 15 Jun when stripe rust was 1-3% severity in the field and the second at boot stage on 25 Jun when stripe rust in the non-treated plots reached 10-20% 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 on whole plot) was assessed from each plot on 15 Jun, 27 Jun, 5 Jul, 13 Jul (data not shown), and 23 Jul or on the same day and 10, 22, 28, and 38 days after the first fungicide application, respectively. Plots were harvested on 16 Sep 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. The first fungicide was applied as stripe rust began to develop; the disease reached 100% severity about one month after the first application. All fungicide treatments with the first application on 15 Jun significantly reduced rust severity when data were recorded on 27 Jun, compared to the non-treated control at boot stage. The Relative AUDPC values of all treatments were significantly less than the non-treated control and were significantly different among some of the treatments. With few exceptions, the treatments with two applications provided better control of stripe rust than the treatments with one application, and the treatment of one early application at jointing stage resulted in better control than those of one late application at boot stage. All treatments significantly increased test weight compared to the non-treated control. All treatments significantly increased grain yield. Among all treatment, Alto 4 fl oz/A (jointing-15 Jun) followed by Quilt 14.0 fl oz/A (boot-25 Jun) had the highest yield, which was 22.5 bu/A (55.4%) more than the non-treated control, whereas Prosaro 5.0 fl oz/A (boot-25 Jun) produced the lowest yield, which was 6 bu/A (14.8%) more than the non-treated control.