Soybean Fungicide Decision Guide
Scout for foliar diseases in soybeans just prior to R3 and answer the following questions when considering an application of foliar fungicide:
What has the Weather Been Like?
How Susceptible is the Variety?
Frogeye leaf spot
- Symptoms appear as light gray centers surrounded by dark borders.
- Yield losses can reach 30% with a severe infection.
- Infection occurs when spores from infected residue are splashed onto the leaves.
Septoria brown spot
- Disease starts in the lower canopy.
- Spots are small, dark brown and irregularly shaped.
- Warm, wet weather favors the development of the disease.
Asian soybean rust
- Disease does not overwinter in the Midwest.
- Spores are carried by southern storms.
- Extended periods of cool, wet weather or high humidity favor the disease.
Does the Field have a History of Disease?
- Some field locations may have a history of greater foliar disease severity.
- River bottoms, low areas or fields surrounded by trees may be more prone to foliar diseases.
What was the Previous Crop?
- Foliar pathogens survive on soybean stubble.
- Risk of foliar diseases increases when a field is planted with soybeans consecutive years.
- For best results, make a fungicide application to soybeans at growth stage R3 (pods are 3/16 inch long at one of the four uppermost nodes.)
- A spray volume of at least 15 gallons/acre (for ground applications) will provide the best coverage.
- For aerial applications, use a volume of 5 gallons/acre.
Average yield response for fungicide and insecticide
treatments evaluated in 2004 to 2008 studies
|Headline R3 + R5
1 Always read and follow label directions. Consult your local ag chem retailer for specific rates and recommendations.
2 Number of comparisons.