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Trouble Shooting Tips and Common Field Problems
AUTHOR
Eric P. Prostko
Professor and Extension Weed Specialist
University of Georgia
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TABLE OF CONTENTS
Trouble Shooting Tips and Common Field Problems
My Approach
This is obvious (paraquat drift)!
This is obvious (auxin injury)!
This is not obvious! (stubby root nematode)
Nematode Distribution in Georgia
Why pick on herbicides?
Herbicide Injury???
Herbicide Injury or Nematodes???
Herbicide Injury??
Herbicide Injury or Fertilizer Injury?
Roundup Drift?
Roundup Drift or LCB??
Valor Injury?
Valor Injury or Soil pH/Zn?
Valor Injury?
Herbicide Injury or Soil pH/Zn?
Soil pH is the key!
Herbicide Injury?
Herbicide Injury or Soil Fertility
Herbicide Drift?
Herbicide Drift or Potassium?
Herbicide Injury??
Herbicide Injury or Disease?
Herbicide Injury?
Herbicide Injury or Nutritional? Yellow Flash
Likely Cause of Glyphosate Yellow Flash
Herbicide Injury?
Herbicide or Nutritional? Boron Toxicity (2019)
Glyphosate Mishaps Again in 2019
Peanut Yield Loss Caused By Glyphosate Applied 75-105 DAP in Georgia.
Is this glyphosate? No, it’s diuron!
Peanut (GA-06G) Yield Loss (%) From Diuron 4L
Sometimes you strike out!
Before You Call or Send Pictures
A good approach to field problems?
Questions?
SLIDE CONTENTS
Trouble Shooting Tips and Common Field Problems Eric P. Prostko, Ph.D. Professor and Extension Weed Specialist Department of Crop & Soil Sciences
My Approach Obvious or not? Patterns Crop history Things you can easily prove or rule out pH fertility nematodes
This is obvious (paraquat drift)!
This is obvious (auxin injury)!
This is not obvious! (stubby root nematode)
Nematode Distribution in Georgia Source: B.B. Brodie. 1976. Journal of Nematology 8:243-247. Sting - July Lesion - March Stubby - February
Why pick on herbicides? Herbicides applied on all crops Companies have money Could not be anything I did or didn’t do! I grid sampled and results were fine!
Herbicide Injury???
Herbicide Injury or Nematodes??? 796-Rootknot nematodes/sample 50+ is a problem
Herbicide Injury??
Herbicide Injury or Fertilizer Injury? Phosphite Fertilizer
Roundup Drift?
Roundup Drift or LCB??
Valor Injury?
Valor Injury or Soil pH/Zn? July 2007 pH = 5.04 Zn = 14-17 lbs/a
Valor Injury?
Herbicide Injury or Soil pH/Zn? June 2010 pH = 4.8 Zn = 14 lbs/A
Soil pH is the key!
Herbicide Injury?
Herbicide Injury or Soil Fertility Old Pasture, no fertilizer was applied, medium soil test K (40 lbs/A) but K deficient (was 0.34% should be 1.7-3.0%) leaf sample
Herbicide Drift?
Herbicide Drift or Potassium? Soybeans are a BIG user of potash (1.14 lbs K20 removed/bushel)
Herbicide Injury?? Johnson County August 2010
Herbicide Injury or Disease? Johnson County August 2010 Anthracnose
Herbicide Injury?
Herbicide Injury or Nutritional? Yellow Flash Soil Analysis pH = 6.6 Mg = 138 lbs/A (high) Mn = 18 lbs/A (S) Zn = 4 lbs/A (S) Plant Analysis N = 4.94% (4.25-5.00) Mg = 0.44% (0.25-0.80) Mn = 54 ppm (15-200) S = 0.25% (0.20-0.60)
Likely Cause of Glyphosate Yellow Flash Degradation of glyphosate to AMPA AMPA reduces chlorophyll content in soybean AMPA = aminomethylphosphonic Acid
Herbicide Injury?
Herbicide or Nutritional? Boron Toxicity (2019) 350 ppm B in leaf tissue (20-60 ppm = sufficient; 100+ ppm = toxic)
Glyphosate Mishaps Again in 2019 June 28 BS
Peanut Yield Loss Caused By Glyphosate Applied 75-105 DAP in Georgia. Glyphosate Rate (5.5 lb ai/gal) – oz/A Yield Loss (%) 2
Is this glyphosate? No, it’s diuron! 5900+ lbs/A Planting Date: April 20 Sprayed: June 7 Picture: June 20 Tift Co. 2018
Peanut (GA-06G) Yield Loss (%) From Diuron 4L Time of Application (DAP) LSD (0.10) = 9 PE-02-19
Sometimes you strike out! Candler County, 2010
Before You Call or Send Pictures At the very least … Last year’s crop Last year’s pesticides This year’s crop and variety This year’s pesticides applied Last pesticide in sprayer Your awesome if you have… Soil Test Results Nematode Results
A good approach to field problems? “Eliminate the impossible. Whatever remains, however improbable, must be the truth.” Sherlock Holmes (i.e. Sir Arthur Conan Doyle) “The Sign of the Four”
Questions? www.gaweed.com