Submitted to: Plant Disease Management Reports
Publication Type: Other
Publication Acceptance Date: 9/19/2007
Publication Date: 10/7/2007
Citation: Mueller, T.A., Miles, M.R., Hartman, G.L., Levy, C. 2007. Evaluations of fungicides and fungicide timing for the control of soybean rust at Zimbabwe, 2005-2006. Plant Disease Management Reports 1=FC103.
Technical Abstract: SC Siesta soybean seeds were planted at Rattray Arnold Research Station in Enterprise Land near Harare, Zimbabwe on 10 Dec 2005 in four row plots, 20 ft. long, with 30 in row spacing and two rows of border. the experimental design was a randomized complete block design with four replications. Treatments consisted of Headline 2.09EC, Folicur 3.6F, Quilt 1.67SC applied at growth stage R1, R3, R5 with either one, two or three applications plus Folicur 3.6F and Headline 2.09EC together or in sequence. Fungicides were applied at 55, 70, and 85 days after planting (DAP) at 15 gallons water per acre with a hand-operated back pack sprayer fitted with a pressure regulator set to 44 psi and equipped with Lurmark F110/1.6/3 flood-jet nozzles spaced 20 inches apart. Soybean plants were rated for severity using a scale based on the percentage of soybean rust covering the leaves in the lower, middle, and upper canopy 84, 99, and 114 DAP. The ratings from these dates were used to calculate the area under the disease progress curve (AUDPC). The average of the lower, middle, and upper canopy was used for analysis. the middle two rows of each plot were harvested at 126 DAP and the yield was adjusted to 13 percent moisture. Soybean rust was first observed 85 DAP, so the first two fungicide applications wereapplied as a protectant and the third application was applied curatively. The disease pressure was relatively high. There were significant differences among treatments fo soybean final rust severity, AUDPC, seed weight, and yield. There was significantly less soybean rust for 16 of the 23 treatments and all of the treatments had significantly less overall rust (UDPC) than the untreated control. All the treatments had greater seed weight than the untreated control, and 15 of the 23 treatments had higher yield than the untreated control. No phytotoxicity was observed for any treatments.