Submitted to: Plant Disease Management Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 4, 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 barley during the 2009 crop season. The experimental field near Pullman, WA was planted with a susceptible spring barley cultivar, Morex, 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 applied at the late jointing stage on 10 Jun significantly prevented rust development. Of the 15 fungicide treatments, six significantly increased both grain test weight and yield; and two significantly increased grain yield. The information should be useful for control of stripe rust on barley.
Technical Abstract: The study was conducted in a field with Palouse silt loam near Pullman, WA. Urea (46-0-0) was applied at 60 lb/A at the time of cultivation. Susceptible ‘Morex’ spring barley 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 09 when barley 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 when there was no sign of rust. To create adequate stripe rust, sporulating seedlings of susceptible ‘Steptoe’ barley that had been inoculated with a mixture of barley stripe rust races collected from the same location in 2008 and grown in a greenhouse were transplanted into the field on 5 Jun. The second fungicide application timing at late jointing was done on 10 Jun when 1% stripe rust was observed in some plots. The third fungicide application timing at boot stage was done on 27 Jun when stripe rust severity ranged from 0 to 50%. 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 just before the third fungicide application timing and 9 Jul, 20 Jul, and 26 Jul or 12, 23, and 29 days after the third fungicide application, 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 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 applied at the late jointing stage on 10 Jun significantly prevented rust development when recorded on 26 Jun. Twelve days after the third fungicide application timing, rust severities were significantly less than that of the non-treated control in all fungicide treated plots, and the severity differences remained significant 29 days after the third fungicide application timing for the treatments of 14 fl oz/A Topguard at late jointing stage, 5 fl oz/A Evito T, Quilt, Quilt Xcel, Tilt, and Quadris. Relative AUDPC values of all treatments were significantly less than that of the non-treated control except the treatments of 7 and 10 fl oz/A Topguard at boot stage. Of the 15 fungicide treatments, six (the two-application treatment of Topguard, the two-application treatment of Evito, Quilt, Quilt Xcel, Tilt, and Quadris) significantly increased both grain test weight and yield; and two (Topguard at 10 fl oz/A and late jointing stage and Evito at 2 fl oz/A) increased grain yield.