Submitted to: Plant Disease Management Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2010
Publication Date: N/A
Interpretive Summary: A total of 15 fungicide treatments were tested for their efficacy in control of stripe rust on spring wheat during the 2009 crop season. The experimental field near Pullman, WA was planted with a susceptible spring wheat cultivar, Lemhi, on April 30, 2009. 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 four 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 compared with the non-treated check, but had significant differences in efficacy. Of the 15 fungicide treatments, 9 significantly increased grain test weight. All fungicide treatments significantly increased grain yield by 25.3% to 60.0%. The information should be useful for control of stripe rust on spring 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 ‘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 09. 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 1 Jun when wheat plants were at early jointing stage. Before the first fungicide application, the field was divided into individual plots of 5 ft (4 rows) in width and 16.6-18.0 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 was done on 1 Jun and the second timing on 10 Jun when there was no sign of rust. The third fungicide application timing at boot stage was done on 27 Jun when stripe rust severity ranged from 1 to 5%. 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 26 Jun, 9 Jul, 20 Jul, and 26 Jul or 1 day before and 12, 23, and 29 days after the third fungicide application timing, respectively. Plots were harvested on 10 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 9 Jul compared with the non-treated control. Differences in stripe rust severity between the fungicide and non-treated control treatments remained significant 23 days after the third fungicide application timing for all treatments except the treatments of Topguard at 7 and 14 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 two treatments of Evito T, together with the treatments of Quilt, Quilt Xcel, Tilt, and Quadris, were in the best ranking group for controlling stripe rust. Of the 15 fungicide treatments, 9 significantly increased grain test weight. All fungicide treatments significantly increased grain yield by 25.3% from 14 fl oz/A Topguard at late jointing stage to 60.0% from Quilt Xcel.