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What Every UGA County Agent Should Know About Weed Science

AUTHOR
Eric P. Prostko
Professor and Extension Weed Specialist
University of Georgia

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TABLE OF CONTENTS
  1. What Every UGA County Agent Should Know About Weed Science
  2. General Thoughts
  3. Herbicide Application Methods
  4. Herbicide Application Methods
  5. What Every UGA County Agent Should Know - I
  6. What Every UGA County Agent Should Know - II
  7. Water pH and major cation concentrations of South Georgia Wells from July 1, 2014 to May 2, 2017
  8. Atrazine 4L @ 2 qts/A + COC @ 1% v/v Applied to 4"-9" Palmer Amaranth (6" average) Photo 13 DAT
  9. What does ALS mean?
  10. Commonly Used ALS Herbicides
  11. Insecticide/Herbicide Interactions
  12. Guidelines for Herbice Use with Counter 20G Insecticide
  13. Counter 20CR @ 6 oz/A (INFR) FB Steadfast 75WG @ 0.75 oz/A + NIS @ 0.25% (V3-V4)
  14. Field Corn (DKC 66-97) Yield Response to Counter fb Steadfast - 2012
  15. Counter 15G (INFR) fb Halex GT + Atrazine + AMS + NIS (V4)
  16. Field Corn Hybrid Yield Response to POST Applied Acuron or Halex GT with/without Counter INFR - 2017
  17. ALS-Sensitive Field Corn Hybrids
  18. Texas Panicum vs. Crabgrass
  19. photo
  20. Metribuzin on soybean Sencor/Lexone
  21. Metribuzin Use (%) - US Soybeans (NASS) Commercial Sale of Sencor began in 1973
  22. Metribuzin Injury
  23. Glyphosate Yellow Flash
  24. Likely Cause of Glyphosate Yellow Flash
  25. Recent Research on Glyphosate and Mineral Accumulation
  26. Valor Great Weed Control vs. Crop Injury
  27. Valor Injury in Peanut
  28. Valor Injury @ (6 oz/A) 16 DAT
  29. Valor SX 51WG Injury - 2018
  30. Peanut Yield Response to Valor - 2009
  31. Peanut Yield Response to Valor 51WG - 2013
  32. Valor Effects on Peanut Yield - High Moisture Conditions - 2018
  33. Cadre/Cotton
  34. Cadre/Impose Rotational Restrictions
  35. Dual/Warrant Injury on Sorghum
  36. Herbicide Carryover or Nematodes
  37. Brooks Co. - 2014
  38. Peanut/pH/Zinc
  39. Recent Picloram Episodes - 2016
  40. Grazon P+D
  41. Peanuts/Picloram UGA Results
  42. Glyphosate/Peanuts
  43. Questions/Comments



SLIDE CONTENTS
  1. What Every UGA County Agent Should Know About Weed Science Eric P. Prostko Extension Weed Specialist Dept. of Crop & Soil Sciences
  2. General Thoughts Herbicides are unpredictable influenced by everything: sprayer, soil type, temperature, moisture, humidity, weed species, stage of growth, etc. etc. when things go bad, they can go really bad! fungicides/insecticides rarely (never?) kill crops Herbicides do not guess do not assume share only results based on repeatable sound science
  3. Herbicide Application Methods Preplant Incorporated (PPI) Preemergence (PRE) Postemergence (POST) Cracking Early-Post (EPOST) Late-Post (LPOST) Lay-By or Post-Directed
  4. Herbicide Application Methods
  5. What Every UGA County Agent Should Know - I Water pH and hardness are not the same thing atrazine is awesome ALS Herbicides OP/ALS/HPPD/Hybrid Interactions Know your grasses metribuzin is awesome glyphosate does not cause nutrient deficiencies
  6. What Every UGA County Agent Should Know - II Valor will cause peanut injury but so what! No way to predict Cadre carryover to cotton! Lime/pH other ALS herbicides (Staple, etc.) Use Concep treated seed with Dual or Warrant on grain sorghum Nematodes and soil fertility problems cause more issues than herbicide carryover. Glyphosate/picloram/peanuts
  8. Atrazine 4L @ 2 qts/A + COC @ 1% v/v Applied to 4”-9” Palmer Amaranth (6” average) Photo 13 DAT
  9. What does ALS mean? Acetolactate synthase (ALS) Acetohydroxyacid synthase (AHAS) chloroplast enzyme needed to form certain amino acids Valine, leucine, isoleucine Herbicide families Imidazolinone, sulfonanalide, benzoates, sulfonylurea
  10. Commonly Used ALS Herbicides Accent Ally/Cimarron Beyond Cadre Classic Envoke Express Finesse FirstRate Harmony Extra Maverick Pro Osprey Permit/Sandea Powerflex Pursuit Python Staple Steadfast Q Strongarm
  11. Insecticide/Herbicide Interactions Insecticides Organophosphates (OP’S) Counter, Lorsban, Thimet Herbicides Steadfast Q Capreno Halex GT Sandea Why? overload the plant’s ability to metabolize chemicals
  13. Counter 20CR @ 6 oz/A (INFR) FB Steadfast 75WG @ 0.75 oz/A + NIS @ 0.25% (V3-V4) CN-06-12 DKC 66-97 15 DAT
  14. Field Corn (DKC 66-97) Yield Response to Counter fb Steadfast - 2012 CN-06-12 Bu/A Treatment LSD 0.10 = 26 CV = 12.82 -43.5%
  15. Counter 15G (INFR) fb Halex GT + Atrazine + AMS + NIS (V4) DKC 62-08 P1794VYHR CN-07-17 April 24 6 DAT
  16. Field Corn Hybrid Yield Response to POST Applied Acuron or Halex GT with/without Counter INFR - 2017 LSD 0.10 = 5 CV = 2.4 CN-07-17 *21,606 plant population
  17. ALS-Sensitive Field Corn Hybrids Dekalb WARNINGS DKC 62-05 DKC 62-06 DKC 62-08 DKC 63-44 DKC 63-47 DKC 63-55 DKC 64-69 CAUTIONS 65-17, 65-18, 65-20 70-01, 70-03 RX940, RX940RR2 Pioneer WARNINGS P1324HR P1360 P1360AM P1360CHR P1360HR P1739R P1739YR CAUTIONS P1637R, P1637VYHR, P1637YHR P1690,P1690HR, P1690R P2088R, P2089YHR
  18. Texas Panicum vs. Crabgrass WSSA Fringe of hairs membranous Texas panicum Southern crabgrass
  20. Metribuzin on soybean Sencor/Lexone Not a PPO (Valor or Reflex) triazine Good on pigweed and sicklepod Can be applied PPI Dryland fields? Issues soil texture, OM, pH Varieties Rotations Company support Lack of incentive at dealer level TriCor 75DF Metribuzin 75DF
  21. Metribuzin Use (%) – US Soybeans (NASS) Commercial Sale of Sencor began in 1973 RR Command – 1985, Scepter - 1986, Pursuit - 1989
  22. Metribuzin Injury
  23. Glyphosate Yellow Flash
  24. Likely Cause of Glyphosate Yellow Flash Degradation of glyphosate to AMPA AMPA reduces chlorophyll content in soybean AMPA = aminomethylphosphonic Acid
  25. Recent Research on Glyphosate and Mineral Accumulation “Glyphosate is unlikely to cause macro and micronutrient deficiencies in soybean if soil nutrient levels are properly maintained.” Henry, R.S, K.A. Wise, and W.G. Johnson. 2011. Glyphosate’s effect upon mineral accumulation in soybean. Online. Crop Management doi:10.1094/CM-2011-1024-01-RS. “Considering the available data, growers are unlikely to need Mn fertilizers just because they use glyphosate on GR soybeans.” Duke, S.O., J. Lydon, W.C. Koskinen, T.B., Moorman, R.L. Chaney, and R. Hammerschmid. 2012. Glyphosate Effects on Plant Mineral Nutrition, Crop Rhizosphere, Microbiota, and Plant Disease in Glyphosate-Resistant Crops. J. Agric. Food Chem. 60:10375-10397
  26. Valor Great Weed Control vs. Crop Injury
  27. Valor Injury in Peanut
  28. Valor Injury @ (6 oz/A) 16 DAT PE-08-09 May 22, 2009 PD: May 5 Rainfall Events: May 5 = 0.04” May 14 = 0.56” May 15 = 0.16” May 16 = 0.01” May 17 = 0.51” May 20 = 0.07” May 21 = 0.59” May 22 = 0.58” May 23 = 0.24” May 24 = 0.13” May 25 = 0.20” May 26 = 0.89” May 28 = 0.05” June 3 = 0.08” June 4 = 0.56” June 5 = 0.77” 30 day rainfall total from planting = 5.44”
  29. Valor SX 51WG Injury - 2018 PE-06-18 May 23 16 DAP 3.11” (R/I) 3 oz/A 6 oz/A
  30. Peanut Yield Response to Valor - 2009 PE-08-09 Averaged over 3 varieties (GA Green, GA-06G, GA-07W) Weed-free LSD 0.10 = 185
  31. Peanut Yield Response to Valor 51WG - 2013 PE-14-13 GA-06G Averaged over 3 planting dates (April 16, April 29, May 13) Weed-free P=0.4015
  32. Valor Effects on Peanut Yield - High Moisture Conditions - 2018 PE-09-18 Weed-free P = 0.7674, CV = 11.3 *averaged over 4 Dual Magnum rates 11.315” rainfall/ irrigation first 30 DAP
  33. Cadre/Cotton
  34. Cadre/Impose Rotational Restrictions
  35. Dual/Warrant Injury on Sorghum
  36. Herbicide Carryover or Nematodes Burke County April 2017 Stubby Root Nematodes 21/100cm3 of soil >9 is threshold
  37. Brooks Co. - 2014 Low pH = 5.3 Very high Zn = 25 lbs/A
  38. Peanut/pH/Zinc
  39. Recent Picloram Episodes - 2016 Mitchell County (GA) June 20, 2016 Baldwin County (AL) June 23, 2016
  40. Grazon P+D Picloram (0.54 lb/gal) and 2,4-D (2 lb/gal) Picloram was first introduced in 1963 as Tordon 101 WSSA MOA #4 (synthetic auxin) broadleaf annual and perennial weeds in rangeland and permanent grass pastures Picloram has average field half-life of 90 days (20-300 day range)
  41. Peanuts/Picloram UGA Results 1/10th X rates of Grazon P+D reduced peanut yields by 11% 1/100thX rates of Grazon P+D caused injury symptoms but not yield loss.
  42. Glyphosate/Peanuts
  43. Questions/Comments