Submitted to: Phytopathology News
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2006
Publication Date: 6/1/2006
Citation: Mueller, T.A., Morel, W., Hartman, G.L. 2006. Effect of timing of fungicide applications on development of soybean rust [abstract]. Phytopathology News.96:S82.
Technical Abstract: Fungicides are an important part of the control of soybean rust, and the timing is critical for effective and economic disease management. The objective of this study was to determine the efficacy of different fungicide classes applied at different times before and after soybean rust inoculation. Four fungicides were evaluated: two triazoles, a strobilurin, and a combination of triazole and strobilurin. All four fungicides significantly reduced the number of rust lesions compared to the unsprayed control at all application times. When applied preventatively, all four fungicides reduced lesions, but the stobilurin and one triazole did not protect as well as the combination and the other triazole when applied 6 days before inoculation, and at 0 and 3 days before inoculation there were no significant differences. When fungicides were applied curatively, soybean leaves had very few lesions (<1 per leaflet) when applied 0 and 3 days after inoculation, and had some lesions (1 to 7 per leaflet) 6 days after inoculation. In general, fungicide efficacy for all of the fungicides decreased either as the duration of time between application of the fungicide to inoculation increased (preventative activity) or as the duration of time between inoculation to application of fungicides (curative activity) increased.