Following the confirmation of rust on sentinel plots in Alabama, Auburn Extension plant pathologist Ed Sikora is advising producers in south and south-central Alabama to "strongly consider a tank-mix or a pre-mix of a triazole and strobilurin. We just don't know how far it's moved up."
Sikora says spraying with rust fungicides is especially critical for soybean growers in those areas if their soybeans are blooming or beyond. He adds that northern Alabama growers should be on alert.
Rust typically surfaces from the flowering stage onward, but can appear sooner. Soybean specialists urge that fungicides must be applied early to combat the disease. And, producers who are putting out a fungicide at R-1 to R-3 must realize if rust comes in, they could still be looking at another application.
Well-known soybean researcher Monte Miles says if the disease is not in your field or in your county, but is expected, you can use a preventive or protectant fungicide, which are the strobilurin fungicides. However, if the disease is present or nearby, you are limited to a triazole or triazole-strobilurin mix. In those instances, he suggests growers should make the first application at or near flowering and plan on making a second application 14 to 20 days after the first. Sprays must penetrate the soybean canopy to have any effect on the disease, which generally appears on the lower leaves.
Specialists are also still encouraging producers not to panic and say the alert system is working. Producers are advised to continue scouting diligently and listen for Extension recommendations.