Cotton Response to Topical Fungicide Application

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Cotton Response to Topical Fungicide Application

• Darrin M. Dodds1
• C. L. Main2, L. T. Barber3, J. E. Woodward4, R.
  Boman4, J. Whitaker5, K. Edmisten6, N. W.
  Buehring1, and T. Allen1.
• Mississippi State University1, The University of
  Tennessee2, University of Arkansas3, Texas
  AgriLife Extension Service4, University of
  Georgia5, North Carolina State University6

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Introduction

• Extension Cotton Specialists Working Group
• Research initiated in response to
• Pyraclostrobin (Headline) 2007
• Azoxystrobin (Quadris) 2008
• Incidence of foliar disease over past several
  growing seasons

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Common Diseases

• Alternaria lesions with brown or purple margins
• Older lesions have concentric rings with center
  falling out in some
• Cercospera small red lesions that enlarge and
  have white to
• brown center
• Avoid all stress esp. potassium, destruction of
  residue
• Ascochyta light brown lesions that coalesce on
  leaves
• Lesion have dark brown borders
• Stemphylium - small circular brown lesions with
  concentric rings
• Older lesions have a white center which can drop
  out.
• Helminthosporium leaf spot

Sciumbato 2009
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Loss Due to Disease 2008
Disease State State State State State
AL AR GA LA MS
Foliar Diseases Yield Reduction 0.10 -- 3.5 Trace 4
Bales Lost 625 -- 66,763 -- 32,500

Boll Rots Yield Reduction 4 2 1 6 4
Bales Lost 25,031 30,337 19,075 20,241 32,500

Total Loss Yield Reduction 4.1 2 4.5 6 8
Bales Lost 25,656 30,337 85,838 20,241 65,000

Dollars Lost 0.65 per pound 8.0 million 9.5 million 26.8 million 6.3 million 20.3 million
Blasingame et al. 2009
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Leaf Spot Disease and Yields

• Defoliation from leaf spot diseases reduced by up
  to 85 following fungicide application
• Not always the case
• Preventative fungicide applications can be
  effective in reducing foliar disease
• Minimal effect on yield
• Application of fungicide in the absence of
  disease did not impact yield

Kemerait et al. 2009 Padgett et al. 2007 Woodward
et al. 2009
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Fungicide Effects on Hardlock

• Hardlock
• Thought to occur due to interaction of Fusarium
  spp. and flower thrips
• Results of fungicide application to control
  hardlock have been mixed
• Decreased incidence of hardlock and increased
  yield following Quadris application

Lawrence et al. 2006 Woodward et al. 2009
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Fungicide Effects on Hardlock

• Yield increases following fungicide application
  have been observed
• Fungicide application when hardlock occurrence is
  lt30 is ineffective
• Limited utility of fungicides for control of
  hardlock
• No yield response due to foliar application

Jones et al. 2008 Padgett et al. 2007 Mailhot et
al. 2008 Woodward et al. 2009
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Justification

• Previous research has yielded mixed results
• Warrants further study to determine proper
  utility
• Previous research is limited
• Increased sales pressure
• Tremendous pressure to make every dollar count

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Materials and Methods

• Small plot research
• RCBD 4 replications
• Participating states
• Arkansas
• Georgia
• Mississippi
• North Carolina
• Tennessee
• Texas

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Treatments
Common Name Trade Name Application Timing Application Code Application Rate Application Rate
Kg ai ha-1 oz prod ac-1
Azoxystrobin Quadris 1st Bloom A 0.11 12
1st Bloom A 0.11 6
14-21 DAA B 0.11 6
1st Bloom A 0.11 6
14-21 DAA B 0.22 12
Pyraclostrobin Headline 1st Bloom A 0.11 12
1st Bloom A 0.11 6
14-21 DAA B 0.11 6
1st Bloom A 0.11 6
14-21 DAA B 0.22 12
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Materials and Methods

• Locally adapted varieties utilized
• All agronomic and pest management practices
  performed according to local standards
• Data analyzed using Proc Mixed
• Data pooled over environments

• Plant height
• Total nodes
• Hardlock
• Gin turnout
• Yield
• Fiber quality

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Figure 1. Untreated cotton foliage
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Figure 2. Quadris 6 oz early bloom 6 oz 21 d.
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Figure 3. Headline 6 oz early bloom 6 oz 21 d.
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End of Season Plant Height
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Growth and Development
Fungicide Rate Total Nodes Hardlock Turnout
-------- -------- ------------------- ------------------- ------------------- -------------------
Quadris 12 oz 17 25 40.0
6 6 oz 18 22 40.5
6 12 oz 17 21 40.3
Headline 12 oz 18 21 39.2
6 6 oz 18 25 40.8
6 12 oz 18 22 40.1
Untreated -- 18 24 39.5
p p 0.09 0.48 0.006
LSD (0.05) LSD (0.05) NS NS 0.01
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Yield
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Fiber Quality
Fungicide Rate Mic Staple Strength Uniformity
------inches------ ------ g tex-1 ------- ------- -------
Quadris 12 oz 4.0 1.16 30.9 82.4
6 6 oz 4.0 1.17 29.7 82.1
6 12 oz 4.1 1.17 30.5 83.0
Headline 12 oz 3.9 1.15 29.6 82.1
6 6 oz 4.2 1.14 30.2 82.3
6 12 oz 4.1 1.14 29.9 82.3
Untreated -- 4.1 1.15 30.0 82.5
p p 0.58 0.04 0.001 0.1773
LSD (0.05) LSD (0.05) NS 0.02 0.6 NS
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Return on Investment
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Conclusions

• Fungicides can control foliar disease
• Application timing is critical
• No differences in plant growth and development
• No yield benefits
• No fiber quality benefits
• More research needed

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Discussion

• Important to determine cause of foliar disease
  and/or boll rot
• Disease pressure usually exacerbated by other
  factors
• Fertility
• Foliar disease often associated with potassium
• Boll rot can be enhanced by excess nitrogen
• Are low nutrient levels in the soil the culprit?
• What about adequate nutrients in the soil and
  shortages in leaf tissue?

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Discussion

• Peak potassium uptake during 3rd 4th week of
  bloom
• Early maturing, fast fruiting varieties
• Fungicide application is not cheap

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Equivalent Costs
Fungicide Rate Fungicide Cost Equivalent Potash Equivalent Lime
--------------------------------------- w/application ---------------------------------------- --------------------------------------- w/application ---------------------------------------- --------------------------------------- w/application ----------------------------------------
Quadris 12 oz 36.53 111 lbs 1 ton
6 6 oz 42.03 132 lbs 1.2 tons
6 12 oz 57.55 194 lbs 1.6 tons
Headline 12 oz 38.50 121 lbs 1.1 tons
6 6 oz 44.00 142 lbs 1.3 tons
6 12 oz 60.50 205 lbs 1.7 tons
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Take Home Message

• Proper utility of foliar fungicides yet to be
  determined
• Avoid use where not necessary due to resistance
  concerns
• Reduce plant stress
• Maximize profit every dollar spent

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Questions