Update on Foliar Fungicides on Corn and Soybean

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Update on Foliar Fungicides on Corn and Soybean

• P. Vincelli, C. Lee, and D. Hershman
• University of Kentucky

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Strobilurin fungicides labeled for corn and
soybean

• Headline (pyraclostrobin) Corn and soybean
• Quadris (azoxystrobin) Corn and soybean
• Quadris Xtra ( cyproconazole) Soybean (section
  18 for SBR).
• Quilt (premix of azoxystrobin and propiconazole)
  Corn and soybean (section 18 for SBR)
• Stratego (premix of trifloxystrobin and
  propiconazole) Corn and soybean
• Several triazoles available but not thoroughly
  tested in either corn or soybean

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For which corn diseases?
Northern leaf blight
Gray leaf spot
Image by K. Leonard and E. G. Suggs Courtesy of
the American Phytopathological Society
Both survive in infested corn residue.
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For which diseases (contd)?
Common rust usually minor to no effect on yield
Southern rust damaging but very sporadic
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For which soybean diseases?
Brown Spot
Pod and Stem Blight/Anthracnose
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For which soybean diseases?
Cercospora Leaf Blight
Frogeye Leafspot
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Strobilurin fungicides provide excellent disease
control in both corn and soybean.

• Yields are higher when disease levels are
  sufficient to reduce yield in untreated crops.

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Yield differential in corn from a strobilurin
fungicide application in 68 university research
trials through 2006
Yield difference, trt minus untrt (bu/A)
Some trials conducted with susceptible hybrids or
other conditions expected to increase disease
pressure. Data collated by Pioneer Hi-Bred.
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2006 Soybean 74 Headline Trials in Northern
U.S.
20.0
Mean 2.8 bu/A
n 74
15.0
P
gt 0.05
P
0.05
10.0
Average Yield Response to Headline (bu/A)
5.0
0.0
IL, Tams
OH, Ross
Delaware
MO, Alma
ND, Fargo
OH, Wood
WI, Bristol
OH, Hardin
SD, Groton
OH, Henry
WI, Wood 1
WI, Wood 2
OH, Shelby
WI, Green 1
OH, Fayette
ON, Harrow
WI, Green 2
NE, SCAL 1
IN, Davis (S)
IL, Brookport
MO, Dockery
IN, Davis (L)
NE, ARDC 1
MN, Waseca
NY, Waterloo
KY, Princeton
WI, Columbia
MO, Henrietta
IN, SEPAC (L)
IN, Pinney (S)
WI, Stoughton
IN, Pinney (L)
MI, Saginaw B
SD, Brookings
WI, Arlington C
WI, Arlington N
IN, NEPAC (S)
IN, NEPAC (L)
IN, SEPAC (S)
MI, Saginaw S
MO, Richmond
ND, Colfax (S)
MO, Hundley 2
MO, Bradford 1
MO, Hundley 3
MO, Bradford 4
ND, Colfax (L)
NE, Tekamah 1
SD, Watertown
MI, Saginaw C6
MO, Greenley 3
MI, Saginaw C2
MO, Greenley 1
MD, Beltsville C
MO, Henrietta II
MO, Greenley 4
KY, Madisonville
IA, Saratoga R2
MO, Bradford 3
MD, Beltsville N
MN, Lamberton
MO, Higginsville
MO, Henrietta III
IA, Saratoga R4
MD, Keedysville
MO, Richmond II
NY, Seneca Falls
IN, Throckmorton (L)
MD, Queenstown (L)
IN, Throckmorton (S)
MD, Queenstown (IR)
MD, Queenstown (S) N
MO, Hundley-Whaley 1
MD, Queenstown (S) C
-5.0
-10.0
Location
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2004 data courtesy Ron Hines, University of
Illinois DeKalb DKC63-81 (GLS5, NLB3, 1-9
scale where 1best) Planted in in conventional
till continuous corn Application at tasseling
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Is there a yield benefit from strobilurin
fungicide on corn that goes beyond disease
control?

• Test this by evaluating yield in the absence of
  disease

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Hybrids selected for 2007 trials
All ratings were provided by the company. 1-2
Excellent, 3-4 Very Good, 5-6 Good, 7-8
Fair, 9 Poor
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Key information on 2007 trials
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Logan County results, 2007
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Spindletop Farm results, 2007
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Is there a yield benefit from strobilurin
fungicide on corn that goes beyond disease
control?

• To date, most research at UK and beyond does not
  support this notion

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Yield differential in corn from a strobilurin
fungicide application in 68 university research
trials through 2006
Yield advantage of fungicide, bu/A
Yield of untreated corn, bu/A
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Yield differential in corn from a strobilurin
fungicide application in 38 grower strip trials
in 2007
Yield difference, trt minus untrt (bu/A)
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2007 commercial corn strip trials
Yield advantage of fungicide, bu/A
Yield of untreated corn, bu/A
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Variability of Results is a Concern

• Farm C, Field 1, Soybean Test, Henderson KY
• 2005
• Response of 28 strips (24 varieties)
• Mean 10.2 bu/A
• Range 3.3 20.3 bu
• Response of 5 tester strips (CPS 6444NRR)
• Mean 13.4 bu
• Range 9.7 18.9 bu

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Variability of Results is a Concern

• Farm C, Field 1, Soybean Test, Henderson KY
• 2005
• Response of 28 strips (24 varieties)
• Mean 10.2 bu/A
• Range 3.3 20.3 bu
• Response of 5 tester strips (CPS 6444NRR)
• Mean 13.4 bu
• Range 9.7 18.9 bu
• 2007
• Response of 30 strips (26 varieties)
• Mean 3.6 bu/A
• Range -0.5 10.4 bu
• Response of 5 tester strips (Vigoro V44N6RR)
• Mean 3.6 bu
• Range 1.3 8.7 bu

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Economic Variability

• Assume 22 for fungicide and application
• Breakeven
• 9.50 soybeans 2.3 bu/A
• 8.50 soybeans 2.6 bu
• 7.50 soybeans 2.9 bu
• 6.50 soybeans 3.4 bu
• 5.50 soybeans 4.0 bu
• 2005 (Henderson County Example)
• Mean, 10.3 bu Range 3.3 bu 20.3
• 2007
• Mean, 3.6 bu Range 1.3 - 8.7 (40 of strips
  below 2.5 bu response)

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Fulton Co., 2006Unreplicated strips by airplane
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Conclusion

• Fungicides (primarily strobilurins) do increase
  yield when diseases are yield-limiting.
• Expect less than stellar results when disease is
  not limiting yield.
• Apply fungicides to corn or soybean when the
  probability of a response is greatest.
• Avoid applying fungicides when the potential for
  a response is low.

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Climbing the Probability Ladder Factors that
increase the probability of yield response from
fungicides on corn and soybean
Higher probability

• 2nd year corn or soybean
• No-till
• Susceptible hybrid (corn)
• Late planting (corn), early planting, early
  maturity (soybean)
• High yield potential
• Disease activity at tasseling (corn), beginning
  pod (soybean)
• Disease-favorable weather or crop irrigated

Lower probability
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Public concern is a concern

• Acres of corn and soybean sprayed in Kentucky
• 2000
• Corn lt1
• Soybean lt1
• 2007
• Corn 20
• Soybean 25
• Most of KYs and U.S. population is no longer
  rural and the public generally fears use of
  pesticides by farmers.
• Plant Health application of fungicides has
  gotten EPAs attention.