Submitted to: Fungicide and Nematocide Tests
Publication Type: Trade Journal
Publication Acceptance Date: 9/11/2005
Publication Date: 1/10/2006
Citation: Miles, M.R., Hartman, G.L., Levy, C. 2006. Control of soybean rust in an indeterminate cultivar at the gwebi variety testing center, Zimbabwe, 2004-05. Fungicide and Nematocide Tests.
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 due to residual and curative properties of the individual products. However, only 5 of the 19 treatments had significantly greater yield than the unprotected control. 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 Gwebi, Zimbabwe during the 2003-04 growing season. Soybean rust was first recorded in the plots on 8 Mar 05, at 102 days after planting (DAP), after the third fungicide application had been applied, 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 fungicide treatments had significantly lower disease severity and less defoliation than the unprotected control. However, only 5 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, greater defoliation and lower yields than the 3-application program when the program means were compared. The fungicide treatment by application program interaction was not significant. However, there were treatments where there were apparent differences between the 2 and 3- application programs for disease severity, defoliation and yield. These differences show a trend where the residual activity differs among the products. Phytotoxicity was observed on two treatments, Carumba 90SL® at 8.2 fl oz and Rubigan EC® at 11 fl oz.