W. R. Stevenson

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Managing Leaf Blight on Carrots
W. R. Stevenson University of Wisconsin
Madison Plant Pathology Department
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Carrot Alternaria and Cercospora Leaf Blights
Cercospora
Cercospora
Alternaria
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Carrot Alternaria and Cercospora Leaf Blights
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Carrot Alternaria and Cercospora Leaf Blights
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Carrot Alternaria and Cercospora Leaf Blights
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2000 Carrot Variety Trial
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Carrot Variety Trial - 2000 Alternaria and
Cercospora Leaf Blights
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Carrot Variety Trial How do we do the trial?

• Paul Miller Farms, Hancock, WI
• 50 Cultivars and breeding lines
• Known susceptible incl.
• 3 replicates
• Pesticides
• NO fungicides applied
• Standard grower herbicide and insecticide
• Disease ratings ( foliage infection) every 10-14
  days
• Evaluation of treatments
• Disease progress
• Area under disease progress curve
• Yield and value (slicer dicer)

Disease Progress Curve
Relative AUDPC
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Carrot Grading Slicer/Dicer Size Grades

• All carrots are graded into 5 size classes (by
  diameter) or culls (misshapen, rotten, etc.)
• The 5 classes can be regrouped to make size
  classes typical of contracts for slicing carrots
  or dicing carrots

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Carrot Variety Trial Slicing Types Disease
Progress Test Lines with Disease Significantly Lucky B
Slicer Standards
Test Lines
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Carrot Variety Trial Slicing Types - Yield Test
Lines with Disease Significantly
AUDPC
Yield (ton/A)
Slicer Standards
Test Lines
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Carrot Variety Trial Slicing Types -
Value Disease Significantly
AUDPC
Gross Value
Slicer Standards
Test Lines
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Carrot Variety Trial Mini Types Disease
Progress Test Lines with Disease Significantly Lucky B
Slicer Standards
Test Lines
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Carrot Variety Trial Mini Types - Yield Test
Lines with Disease Significantly
AUDPC
Yield (ton/A)
Slicer Standards
Test Lines
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Carrot Variety Trial Dicing Types Disease
Progress Test Lines with Disease Significantly Lucky B
Dicer Standards
Test Lines
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Carrot Variety Trial Dicing Types - Yield Test
Lines with Disease Significantly
AUDPC
Yield (ton/A)
Dicer Standards
Test Lines
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Carrot Variety Trial Dicing Types -
Value Disease Significantly
AUDPC
Gross Value
Dicer Standards
Test Lines
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2000 Carrot Fungicide Trial
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Carrot Fungicide Trial 2000Treatments
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Carrot Fungicide Trial 2000Disease Development
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Carrot Fungicide Trial - Hancock, 2000How do we
do the trial?

• Heritage
• 7 Treatments
• Untreated control
• 6 Fungicide treatments
• D3-23 nozzles, 35 GPA, 40 psi
• 4 replicates
• 7-day schedule
• foliar disease severity rated every 7-10 days
• Evaluation of treatments
• Disease progress
• Area under disease progress curve
• Yield, size grades

Disease Progress Curve
AUDPC
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Carrot Fungicide Trial - 2000 Efficacy and Yield
AUDPC
Total Yield (ton/A)
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Carrot Fungicide Trial - 2000 Efficacy and Yield
AUDPC
Total Yield (ton/A)
lb ai/A
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Carrot Fungicide Trial - 2000 Efficacy and Value
AUDPC
Value (/A)
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and comments . . .