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Impact of Application Timing of Fungicides On the Management of Target Spot Jared Walls R.C. Kemerait, A. Fulmer, C. Perry, F. H. Sanders, S. Newell, L. Newsom University of Georgia Cooperative Extension Research Update Importance of Foliar Diseases

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SLIDE 1

Impact of Application Timing of Fungicides On the Management of Target Spot

Jared Walls R.C. Kemerait, A. Fulmer, C. Perry, F. H. Sanders, S. Newell, L. Newsom University of Georgia Cooperative Extension Research Update

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SLIDE 2

Importance of Foliar Diseases

  • Historically foliar diseases (other than

boll rot) were of minor importance in Georgia

– Cercospora Leaf Spot – Ascochyta Blight – Areolate Mildew – Angular Leaf Spot

  • Exception is Stemphylium Leaf Spot

– Potassium deficiency is underlying cause – Less evidence of effective management with fungicides

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SLIDE 3

Impact of Target Spot

  • Since 2005, growers noticed a disease unrelated

to potassium

  • Symptoms associated with this disease

– Premature defoliation – Severe spots on leaves, bolls, and bracts – Significant yield losses

  • 2008, Corynespora leaf spot was distinguished

from other foliar diseases

  • 2012: FL, AL, NC, SC, and VA
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SLIDE 4

Koch’s Postulates for Proof of Target Spot

  • A. M. Fulmer, J. T. Walls, B. Dutta, V. Parkunan, J. Brock, and R. C. Kemerait, Jr., First Report of Target

Spot Caused by Corynespora cassiicola on Cotton in Georgia, Plant Disease 2012 96:7, 1066‐1066

  • DP 555 and DP 1048
  • Inoculated at 2‐4 leaf stage
  • Incubated in moist chamber at 21° C for 48 hours
  • 100% of inoculated plants showed symptoms
  • No symptoms found on non‐inoculated plants
  • Fungus was re‐isolated, cultured, and confirmed

by morphological characteristics and PCR

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SLIDE 5

Objectives

  • Best application timing for disease

management

– Disease onset – Growth stage (coverage) – Length of protection

  • Quantify the effect that Target Spot has on

yield

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SLIDE 6

Description of Small Plot Trials

  • Randomized and Replicated Studies (4‐6 reps)
  • Trials conducted on research stations in Tifton, Camilla (Stripling) , and Attapulgus

– Camilla: did not cut alley until defoliation (Irrigated and Dryland)

  • PHY 499
  • Fungicides

– Headline (pyraclostrobin) – Twinline (pyraclostrobin + metconazole) – Priaxor (pyraclostrobin + fluxapyroxad)

  • Lee Spider

– 8002 FF – 20 GPA

  • Ratings

– Defoliation (2012) – Yield (2012) – Florida 1‐10 (2013)

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SLIDE 7

2012 Stripling Irrigation Park, Mitchell County

Target Spot

Overhead Irrigation

10 20 30 40 50 60 70 % Defoliation

Dryland

10 20 30 40 50 60 70 % Defoliation

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SLIDE 8

2012 Stripling Irrigation Park, Mitchell County

Target Spot

Overhead Irrigation

979 985 933 1191 1065 985

600 800 1000 1200 1400 1600 Yield (lb/ac)

Dryland

1214 1167 953 1405 1286 1072

600 800 1000 1200 1400 1600 Yield (lb/ac)

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SLIDE 9

2012 Stripling Irrigation Park, Mitchell County

Target Spot 0.0 1.0 2.0 3.0 4.0 5.0 6.0 Severity (1‐6)

LSD=1.15 (P ≤ 0.05)

Planting date = May 3, First Bloom = July 10, Disease was first confirmed around June 20th Last spray before rating: July 24 (3rd Week of Bloom)

Headline: 6 oz. Twinline: 8.5 oz.

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SLIDE 10

2012 Stripling Irrigation Park, Mitchell County

Target Spot 10 20 30 40 50 60 70 % Defoliation LSD=16.95 (P ≤ 0.05)

  • Aug. 1

Headline: 6 oz. Twinline: 8.5 oz.

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SLIDE 11

2012 Stripling Irrigation Park, Mitchell County

Target Spot 10 20 30 40 50 60 70 % Defoliation LSD=23.95 (P ≤ 0.05)

  • Aug. 1
  • Aug. 16

Last spray before rating: August 15 (5th Week of Bloom)

Headline: 6 oz. Twinline: 8.5 oz.

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SLIDE 12

2012 Stripling Irrigation Park, Mitchell County

Target Spot 10 20 30 40 50 60 70 % Defoliation LSD=30.67 (P ≤ 0.05)

  • Aug. 1
  • Aug. 16
  • Sept. 10

Headline: 6 oz. Twinline: 8.5 oz.

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SLIDE 13

2012 Stripling Irrigation Park, Mitchell County

Target Spot 700 800 900 1000 1100 1200 Yield (lb/av) LSD=312.62 (P ≤ 0.05)

Headline: 6 oz. Twinline: 8.5 oz.

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SLIDE 14

2012 Attapulgus REC, Decatur County

Target Spot / Stemphylium

Planting date = May 29, First Bloom = July 30, Disease was first confirmed around Aug 24th Last spray before rating: August 16 (3rd Week of Bloom)

10 20 30 40 50 60 70 % Defoliation LSD=16.15 (P ≤ 0.05) NS

  • Aug. 29

Headline: 6 oz. Twinline: 8.5 oz.

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SLIDE 15

2012 Attapulgus REC, Decatur County

Target Spot / Stemphylium 10 20 30 40 50 60 70 % Defoliation LSD=18.72 (P ≤ 0.05) NS

  • Aug. 29
  • Sept. 11

Last spray before rating: September 4 (5th Week of Bloom)

Headline: 6 oz. Twinline: 8.5 oz.

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SLIDE 16

2012 Attapulgus REC, Decatur County

Target Spot / Stemphylium 10 20 30 40 50 60 70 % Defoliation LSD=16.63 (P ≤ 0.05) NS

  • Aug. 29
  • Sept. 11
  • Sept. 24

Last spray before rating: September 13 (7th Week of Bloom)

Headline: 6 oz. Twinline: 8.5 oz.

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SLIDE 17

2012 Attapulgus REC, Decatur County

Target Spot / Stemphylium 1000 1100 1200 1300 1400 Yield (lb/ac) LSD=255.54 (P ≤ 0.05) NS

Headline: 6 oz. Twinline: 8.5 oz.

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SLIDE 18

2012 RDC Pivot, Tift County

Target Spot / Stemphylium 0.0 1.0 2.0 3.0 4.0 5.0 6.0 Severity (1‐6) LSD=0.77 (P ≤ 0.1)

  • Sept. 18

Planting date = May 7, First Bloom = July 17, Disease was first confirmed around Sept. 5th Last spray before rating: August 31 (7th Week of Bloom)

Headline: 6 oz. Twinline: 8.5 oz.

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SLIDE 19

2012 RDC Pivot, Tift County

Target Spot / Stemphylium 10 20 30 40 50 60 70 % Defoliation LSD=22.88 (P ≤ 0.1)

  • Sept. 18

Last spray before rating: August 31 (7th Week of Bloom)

Headline: 6 oz. Twinline: 8.5 oz.

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SLIDE 20

2012 RDC Pivot, Tift County

Target Spot / Stemphylium 700 800 900 1000 1100 1200 Yield (lb/ac) LSD=187.6 (P ≤ 0.1) NS

Headline: 6 oz. Twinline: 8.5 oz.

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SLIDE 21

Georgia Small Plot Trial Recap

Stripling

  • 3rd week of bloom timing best reduced defoliation
  • Late application protected new growth, but did not help

yields Attapulgus

  • Stemphylium and Target Spot
  • Not much defoliation
  • 11 of 13 treatments had numeric yield increase

Tifton

  • Late timings had best disease control
  • 8 of 11 treatment had numeric yield increases

 200 LB.

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SLIDE 22

2012 Cotton Defoliation Study, Mitchell County

Target Spot 900 1000 1100 1200 1300 1400 1500 1600 DPL 1050 DPL 1137 FM 1740 PHY 367 FM 1944 PHY 375 ST 5458 PHY 499 DPL 1252 Lint (lb/ac) Twinline (6 oz) Untreated

Source: RJ Byrne

Sprayed rows were treated with a single application of Headline during the 6th week of bloom

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SLIDE 23

2012 Cotton Defoliation Study, Mitchell County

Target Spot 900 1000 1100 1200 1300 1400 1500 1600 DPL 1050 DPL 1137 FM 1740 PHY 367 FM 1944 PHY 375 ST 5458 PHY 499 DPL 1252 Lint (lb/ac) P ≤ 0.05 Twinline (6 oz) Untreated

Source: RJ Byrne

Disease was established in the field prior to application

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SLIDE 24

2012 Tidewater AREC, Suffolk VA

Target Spot 10 20 30 40 50 60 % Defoliation P ≤ 0.05

Source: Pat Phipps, Virginia Tech

  • Sept. 12

Planting date = May 17, First bloom = July 23, Disease was first confirmed on August 27 Last spray before rating: August 28 (6th Week of Bloom)

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SLIDE 25

2012 Tidewater AREC, Suffolk VA

Target Spot 10 20 30 40 50 60 % Defoliation P ≤ 0.05

  • Sept. 12
  • Oct. 12

Source: Pat Phipps, Virginia Tech

Planting date = May 17, First bloom = July 23, Disease was first confirmed on August 27 Last spray before rating: August 28 (6th Week of Bloom)

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SLIDE 26

2012 Tidewater AREC, Suffolk VA

Target Spot 1900 2000 2100 2200 2300 Lint (Lb/Ac) P ≤ 0.05

Source: Pat Phipps, Virginia Tech

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SLIDE 27

Florida 1‐10 Scale

  • 1. No disease
  • 2. Few spotted leaves in canopy
  • 3. Few spotted leaves in upper canopy
  • 4. Leaf spotting and ≤ 5% defoliation
  • 5. Leaf spotting and ≤ 25% defoliation
  • 6. Spotted leaves numerous and ≤ 50% defoliation
  • 7. Spotted leaves numerous and ≤ 75% defoliation
  • 8. Numerous leaf spots and ≤ 90% defoliation
  • 9. Few remaining leaves and ≤ 95% defoliation

10.Plants defoliated or dead

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SLIDE 28

2013 Stripling Irrigation Park, Mitchell County

Target Spot 2 4 6 8 10 FLA 1‐10 LSD=0.138 (P ≤ 0.05) NS 17‐Jul

Headline: 6 oz. Twinline: 8.5 oz.

Planting Date = May 8, First Bloom = July 9, Disease was confirmed on July 9 Last spray before rating = July 9th (1st Week of Bloom)

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SLIDE 29

2013 Stripling Irrigation Park, Mitchell County

Target Spot 2 4 6 8 10 FLA 1‐10 LSD=0.988 (P ≤ 0.05) 17‐Jul 6‐Aug.

Headline: 6 oz. Twinline: 8.5 oz.

Planting Date = May 8, First Bloom = July 9, Disease was confirmed on July 9 Last spray before rating = July 25th (3rd Week of Bloom)

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SLIDE 30

2013 Stripling Irrigation Park, Mitchell County

Target Spot 2 4 6 8 10 FLA 1‐10 LSD=0.855 (P ≤ 0.05) 17‐Jul 6‐Aug. 27‐Aug.

Headline: 6 oz. Twinline: 8.5 oz.

Planting Date = May 8, First Bloom = July 9, Disease was confirmed on July 9 Last spray before rating = August 20th (7th Week of Bloom)

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SLIDE 31

Summary

  • Optimal fungicide timing appeared to be first week of

bloom and third weed of bloom

  • Strong trends for numeric yield increases across fungicide

treatments versus untreated check

  • Plots treated with Headline tended to out‐yield plots

treated with Twinline

  • Evidence shows that Target Spot can be controlled with use
  • f fungicides with potential of protected yield
  • Combined results suggest that 200 lb. increase in lint is a

realistic goal with use of fungicides

  • Growers with high risk fields can expect similar results

when using fungicides at proper timing

– UGA Extension will recommend judicious use of fungicides in cotton in 2013

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SLIDE 32

Acknowledgements

  • BASF
  • Attapulgus REC Staff
  • Stripling Irrigation Park Staff
  • Abraham Fulmer
  • Landon Cason
  • Patrick Wilson
  • Lyn Young
  • Jeannette Mixon
  • Jhenylyn Bennett
  • Joy Ouano Carter
  • Ross Fulghum
  • Caleb Clements