Control of stripe rust of spring wheat with various foliar fungicides

Authors: Chen, Xianming; Evans, Conrad; LIU, YUMEI - Washington State University

Submitted to: Plant Disease Management Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2014
Publication Date: 2/10/2014
Publication URL: http://www.plantmanagementnetwork.org/pub/trial/pdmr/reports/2014/CF034.pdf
Citation: Chen, X., Evans, C.K., Liu, Y. 2014. Control of stripe rust of spring wheat with various foliar fungicides. Plant Disease Management Reports. 8:CF034.

Interpretive Summary: A total of 33 foliar fungicide treatments were tested for their efficacy in control of stripe rust on spring wheat during the 2013 crop season. The experimental field near Pullman, WA was planted with a susceptible spring wheat variety on April 18. A randomized complete block design experiment with four replications was used including a non-treated check treatment. Fungicides were applied on two 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 five 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 differences among the treatments. Stripe rust was relatively low on spring crop due to the hot and dry weather conditions, and caused up to 12% yield loss in the non-treated control plots. All fungicide treatments significantly reduced rust AUDPC, but did not significantly increase test weight and grain yield compared to the non-treated control, although significant differences in test weight and yield were observed among the fungicide treatments. Some of the new formulations could be registered for control of stripe rust.

Technical Abstract: The study was conducted in a field with Palouse silt loam under natural infection of stripe rust near Pullman, WA. Susceptible ‘Avocet S’ spring wheat was seeded in rows spaced 14 in. apart at 80 lb/A (99% germination rate) with a drill planter on 18 Apr. 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 (Feeks 5) was done on 17 Jun when stripe rust was 0-1% severity in the field. The second application was done at boot stage (Feeks 10) on 25 Jun when stripe rust in the plots without first fungicide application reached 1-5% severity. A randomized block design was used with four replications. Disease severity (percentage of diseased foliage per whole plot) was assessed from each plot on 17 Jun, 25 Jun, 3 Jul, 18 Jul (data not shown), and 29 Jul or on the day of fungicide application and 8, 16, 31, and 42 days after the first fungicide application timing, respectively. Plots were harvested on 28 Aug 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 (rAUDPC) was calculated as percent of the non-treated control. Rust severity, rAUDPC, 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 and the second application was applied as the disease only reached 1-5% severity in the plots without the first application. Because of the hot and dry weather conditions, stripe rust developed slowly and only reached about 50% severity in the non-treated check plots by the end of the disease season or about 42 days after the first application. All fungicide treatments significantly reduced rust severity compared to the non-treated control at milk stage about 16 days after the first application. The rAUDPC values of all treatments were significantly less than the non-treated control, and only the treatment with Aproach 3 fl oz/A at Feeks 5 was significantly different from the other treatments. Although there were significant differences in test weight among the fungicide treatments, none of the treatments produced test weight significantly different from the non-treated control. Similarly, some of the fungicide treatments (Caramba 4 fl oz/A at Feeks 5 followed by Caramba 4 fl oz/A at Feeks 10, Twinline 6 fl oz/A at Feeks 5 followed by Twinline 9 fl oz/A at Feeks 10, Topguard 7 fl oz/A at Feeks 10, Tilt 4 fl oz/A at Feeks 10, and Quilt 14 fl oz/A at Feeks 10) produced higher yields than Custodia 8.6 fl oz/A at Feeks 10, but none of them produced significantly higher or lower grain yield than the non-treated control as the LSD value was relatively high. The results showed that the low level of stripe rust did not cause significant yield loss and fungicide application was generally not necessary for spring wheat crop in 2013.