Soybean Fungicide Decision Guide

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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
 
 

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
 
 

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.

Table 1. Average yield response for fungicide and insecticide
treatments evaluated in 2004 to 2008 studies.

Fungicide
Treatment
Years
Tested
N 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
Headline R5 2004-06 48 2.7
Quadris R5 2004-06 48 1.6
Headline R3 + R5 2004-06 48 4.6
 

Table 2. Average yield response to fungicide treatments
evaluated in 2007 to 2014 DuPont Pioneer on-farm trials.

Fungicide
Treatment
Years
Tested
N Yield Response
(bu/acre)
Headline 2007-11 109 2.6
DuPont™ Aproach® 2012-14 123 2.7

Fungicide performance is variable and subject to a variety of environmental and disease pressures. Individual results may vary. Always read and follow all label directions and precautions for use when applying fungicides. Labels contain important precautions, directions for use and product warranty and liability limitations that must be read before using the product. Mention of a product does not imply a recommendation. The foregoing is provided for informational use only. Please contact your Pioneer sales professional for information and suggestions specific to your operation. Product performance is variable and depends on many factors such as moisture and heat stress, soil type, management practices and environmental stress as well as disease and pest pressures. Individual results may vary.


 
 
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