Soybean Fungicide Decision Guide

In-Depth Downloads


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?

  • Rainy and/or humid weather is most favorable to foliar diseases.

How Susceptible is the Variety?

  • The greater the disease resistance rating for a variety, the less likely a fungicide application will result in economic benefit.

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.

frogeye leaf spot photo

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.

septoria brown spot photo

 

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.

Asian soybean rust

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

Treatment1 Years
Tested
N2 Yield Response
(bu/acre)
Headline® R1 2007 40 2.3
Headline R3 2004-08 100 3.7
Quadris® R3 2004-08 100 2.9
Folicur® R3 2004-06 48 1.5
Quadris/Warrior® R3 2005-08 88 4.1
Headline/Asana® R3 2007-08 52 5.5
Headline R5 2004-06 48 2.7
Quadris R5 2004-06 48 1.6
Headline R3 + R5 2004-06 48 4.6


1
Always read and follow label directions. Consult your local ag chem retailer for specific rates and recommendations.
2 Number of comparisons.


® Asana XL is a registered trademark of E. I. du Pont de Nemours and Company. Asana® XL is a restricted-use pesticide. Always read and follow label directions.
All products are trademarks of their manufacturers.
 
 
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