Selecting the right fungicide and applying it within the right window of time is pivotal to manage soybean rust.
Determining whether fungicidal management of soybean rust is necessary largely relies on tracking disease spread. If soybean rust has not been identified within 100 miles of your field, preventive measures are not likely needed.¹
However, if you identify soybean rust, fungicide applications applied between the R3 and R5 soybean growth stages typically provide the most consistent yield protection.
Soybean rust damage and yield loss
Once you spot soybean rust in your field, time is money. When fungicides are applied after 10% disease severity (10% of leaves show rust), the effectiveness of the fungicide is significantly reduced, and you’re leaving money on the table due to lost yield. For example, research demonstrated yield reduction of 17% when fungicide application was delayed until one week after soybean rust was first detected. The yield reduction rose to 38% if treatment was delayed two weeks.²
How do you protect from soybean rust?
Soybean traits with genetic resistance to soybean rust have been identified; however, the use of resistant traits has not been an effective long-term strategy for countering yield loss from rust. For long term control, the following fungicide treatments should be considered:
Priaxor® fungicide
Priaxor fungicide offers effective control and consistent yield protection when applied between the R2 and R4 growth stages before disease development. The timing and number of applications needed depends on environmental conditions, including how early in the season the infection sets in, amount of rainfall and average temperature.
Revytek® fungicide
Fast-acting and long-lasting Revytek fungicide gives you proven protection without trade-offs. It should be applied to soybean rust prior to disease development in 14-day intervals, generally between the R2 and R4 growth stages.
- REI: (Field re-entry interval) 12 hours for both Priaxor and Revytek
- PHI: (Pre-harvest interval) 21 days for both Priaxor and Revytek
- Use rate: Priaxor 4 oz/a and Revytek 8 oz/a
- Adjuvant: NIS at 1 pt/100 or COC at 1 pt/a can be used to improve coverage
- Nozzle, Droplet: Flat fan, fine to medium for both Priaxor and Revytek
- Both Priaxor and Revytek can be mixed with other fungicides, insecticides, herbicides and liquid fertilizers.
- Do not apply more than ½ inch per acre water with chemigation
Always read and follow label directions. Keep fungicide resistance in mind as you make selections. Be sure to use more than one mode of action if you plan to apply several fungicides in a growing season.
While you may not be able to keep soybean rust out of your fields, you can stay informed and practice proactive soybean rust management strategies. Tools are available to help you monitor the pathogen’s footprint, like this integrated pest management map. For additional guidance on soybean rust fungicides, management and prevention, remember to consult your seed retailer, a nearby extension office agent or a seed company professional like your regional BASF representative.
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Endnotes
- Rosado Rivera, Yara, and Lindsey Thiessen. “Asian Soybean Rust.” NC State Extension Publications, 2 Sept. 2020, content.ces.ncsu.edu/asian-soybean-rust. Accessed 26 Mar. 2026.
- Giesler, Loren J. “Asian Soybean Rust.” CropWatch, University of Nebraska-Lincoln, cropwatch.unl.edu/plant-disease/soybean/soybean-rust/. Accessed 26 Mar. 2026.
