Control of stripe rust of winter wheat with foliar fungicides, 2009

Authors: Chen, Xianming; Wood, David

Submitted to: Plant Disease Management Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/4/2010
Publication Date: 3/26/2010
Citation: Chen, X., Wood, D.A. 2010. Control of stripe rust of winter wheat with foliar fungicides, 2009. Plant Disease Management Reports 4:CF003.

Interpretive Summary: A total of 15 fungicide treatments were tested for their efficacy in control of stripe rust on winter wheat during the 2008-2009 crop season. The experimental field near Pullman, WA was planted with a susceptible winter wheat cultivar, PS 279, on October 23, 2008. The standard cultural practices including seeding rate, fertilization, and weed control for growing winter wheat crops in the region was used. An randomized complete block design with four replications was used including a non-treated check treatment. Fungicides were applied on different dates and 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 five 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, but with significant differences in efficacy. Relative AUDPC values of all treatments were significantly less than the non-treated check, and were significantly different among some of the treatments. All treatments significantly increased grain test weight and yield by 22.0% to 76.2%. The information is useful for controlling stripe rust on winter wheat.

Technical Abstract: The study was conducted in a field with Palouse 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 ‘PS 279’ winter wheat was seeded in rows spaced 14 in. apart at 60 lb/A (99% germination rate) with a drill planter on 23 Oct 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 13 May 09 when wheat plants were at late tillering stage. Before the first fungicide application, the field was divided into individual plots of 5 ft (4 rows) in width and 16.8-18.0 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 early jointing stage was done on 22 May and the second at late jointing stage when there was no sign of rust. The third fungicide application timing at boot stage was done on 10 Jun when stripe rust of 1% severity was observed in some plots. 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 9 Jun, 17 Jun, 24 Jun, 1 Jul, and 14 Jul or 1 day early and 7, 14, 21, and 34 days after the third fungicide application timing, respectively. Plots were harvested on 5 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 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. All fungicide treatments significantly prevented rust development from 17 Jun through 1 Jul and nine of the treatments maintained rust severity levels significantly less than the non-treated control 34 days after the third fungicide application timing. Relative AUDPC values of all treatments were significantly less than the non-treated control, and were significantly different among some of the treatments. All treatments significantly increased grain test weight and yield. Yield increases ranged from 22.0% from the two-application treatment of Evito to 76.2% from Quadris.