Submitted to: Fungicide and Nematocide Tests
Publication Type: Research Notes
Publication Acceptance Date: 9/1/2005
Publication Date: 12/5/2006
Citation: Miles, M.R., Hartman, G.L., Levy, C. 2006. Control of soybean rust in a determinate cultivar at the Rattray Arnold Research Station, Zimbabwe, 2004-05. Fungicide and Nematocide Tests. 61:FC003. Interpretive Summary: An important aspect to the management of soybean rust is the use of fungicides. This study evaluated fungicide efficacy using two and/or three applications at one location in Zimbabwe. Soybean rust was rated as a percentage of leaf area affected within the center two rows of each plot. Plots were harvested and yields were calculated. Soybean rust occurred late in the growing season but all the fungicides provided some control of the disease. This control was seen in both reduced disease severity and higher yields when compared to an unprotected control. When products were compared in a 2 or 3 application program differences were seen. These differences were due to differences in residual and curative properties at the individual products. This information is useful for those interested in managing soybean rust, and includes soybean growers, industry personnel and crop consultants.
Technical Abstract: Fungicide trials for the management of soybean rust were done at the Rattray Arnold Research Station, Zimbabwe during the 2003-04 growing season. Soybean rust was first recorded in the plots on 10 Mar 05, at 83 DAP, between the second and third fungicide application, thus all treatments were applied as a protectant. The only plots where soybean rust was seen on this date were the unprotected controls where a visual severity of 5% was reported in the lower canopy. There were significant differences among the treatments for AUPDC, defoliation and yield. All treatments had significantly lower disease severity and less defoliation than the unprotected control. However, only 10 of the 19 treatments had significantly greater yield than the unprotected control. The difference between the 2-application program and the 3-application program was also significant; the 2-application program had more severe disease, and greater defoliation than the 3-application program when means were compared. The mean yield of the 2-application program was less then that of the 3-application program, but not significantly. There was a significant treatment by application program interaction with AUDPC but not with defoliation or yield. However, there were treatments where there were apparent differences between the 2 and 3 applications for defoliation and yield. These differences show a trend where the residual activity differs among the products. No phytotoxicity was observed in any treatments.