Cotton Response to Topical Fungicide Application Darrin M. Dodds 1 C. L. Main 2, L. T. Barber 3, J. E. Woodward 4, R. Boman 4, J. Whitaker 5, K. Edmisten.

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

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

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

Loss Due to Disease – 2008

Disease 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

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. 2009Padgett et al. 2007

Woodward et al. 2009

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. 2006Woodward et al. 2009

Fungicide Effects on Hardlock

• Yield increases following fungicide application have been observed

• Fungicide application when hardlock occurrence is <30% is ineffective

• Limited utility of fungicides for control of hardlock– No yield response due to foliar application

Jones et al. 2008Padgett et al. 2007Mailhot et al. 2008

Woodward et al. 2009

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

Materials and Methods

• Small plot research– RCBD – 4 replications

• Participating states:– Arkansas– Georgia– Mississippi– North Carolina– Tennessee– Texas

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

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

Figure 1. Untreated cotton foliage

Figure 2. Quadris 6 oz early bloom + 6 oz 21 d.

Figure 3. Headline 6 oz early bloom + 6 oz 21 d.

End of Season Plant Height

0

10

20

30

40

50

60

70

80

90

100

110

Quadris 12 oz

Quadris 6 + 6 oz

Quadris 6 + 12 oz

Headline 12 oz

Headline 6 + 6 oz

Headline 6 + 12 oz

Untreated

LSD (0.05) = NSD

Fungicide

% o

f U

ntr

eat

ed C

he

ck

5 Locations in 2008 and 2009 p = 0.47

Growth and DevelopmentFungicide 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 0.09 0.48 0.006

LSD (0.05) NS NS 0.01

Yield

0

10

20

30

40

50

60

70

80

90

100

110

Quadris 12 oz

Quadris 6 + 6 oz

Quadris 6 + 12 oz

Headline 12 oz

Headline 6 + 6 oz

Headline 6 + 12 oz

Untreated

LSD (0.05) = NSD

Fungicide

% o

f U

ntr

eat

ed C

he

ck

6 Locations in 2008 and 2009 p = 0.55

Fiber QualityFungicide 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 0.58 0.04 0.001 0.1773

LSD (0.05) NS 0.02 0.6 NS

Return on Investment

-50

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

Quadris 12 oz

Quadris 6 + 6 oz

Quadris 6 + 12 oz

Headline 12 oz

Headline 6 + 6 oz

Headline 6 + 12 oz

Untreated

Fungicide

$ R

etu

rned

6 Locations in 2008 and 2009

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

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?

Discussion

• Peak potassium uptake during 3rd – 4th week of bloom

• Early maturing, fast fruiting varieties

• Fungicide application is not cheap

Equivalent Costs

Fungicide RateFungicide

CostEquivalent

PotashEquivalent

Lime

--------------------------------------- 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

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

Questions