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TITLE    (click title to view slides)
2008 Corn Weed Control Update

AUTHOR
Eric P. Prostko
Extension Weed Specialist
Dept. Crop and Soil Sciences
The University of Georgia

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TABLE OF CONTENTS
  1. 2008 Corn Weed Control Update
  2. Herbicide Resistance Concerns for Field Corn
  3. Glyphosate Resistance Around the World (13 species)
  4. GA Confirmed Glyphosate-Resistant Palmer Sites
  5. GA Confirmed ALS-Resistant Palmer Sites
  6. Triazine Resistant Palmer Amaranth Macon County - 2007
  7. Cotton Herbicides/Corn Rotations
  8. Burndown Control Options
  9. Ryegrass Control - Burndown
  10. Annual Ryegrass Control with Roundup WM
  11. Conventional or RR Systems?
  12. Conventional Systems
  13. Why do you not want to spend the money on an Accent + Atrazine treatment in field corn?
  14. Corn Yield Response to Various POST Herbicide Treatments
  15. Conventional Weed Management Systems - Many Pre-Mixes Available
  16. Post-Directed Options for Field Corn
  17. U.S. Corn Acres Planted to Herbicide Resistant Hybrids
  18. Should you use the RR corn system?
  19. How would I use RR corn systems?
  20. Corn Grain Yield As Influenced by Glyphosate Timing (35 locations)
  21. Texas Panicum Control At Harvest with Single or Split Applications of Roundup WM - II
  22. Corn Yield Response to Single or Split Applications of glyphosate
  23. Preserving the Value of Glyphosate
  24. New Products that have been tested
  25. Callisto
  26. Texas Panicum Control
  27. What about Liberty-Link Corn?
  28. Don’t Forget Liberty-Link Corn!
  29. Morningglory Control in Corn
  30. Pigweed Control in Corn
  31. Corn Yield Losses Caused by Palmer Amaranth Plants When They Emerge with Crop
  32. This is what a 2' pigweed looks like!!!!
  33. Palmer Amaranth Control in Sorghum-Sudangrass Silage
  34. Palmer Amaranth Control in Field Corn (Photo 14 Days after POST)
  35. GR-Palmer Amaranth Control in Field Corn May 31, 2007 (38 DAP)
  36. GR-Palmer Amaranth Control in Field Corn May 31, 2007 (38 DAP)
  37. GR-Palmer Amaranth Control in Field Corn May 31, 2007 (38 DAP)
  38. Sicklepod Control in Corn
  39. Nutsedge Control
  40. Tropical spiderwort (a.k.a. Benghal dayflower) Commelina benghalensis
  41. TSW in Georgia
  42. TSW Control in Field Corn
  43. Post-Harvest Control of Tropical Spiderwort
  44. Post-Harvest Control of Tropical Spiderwort
  45. Johnsongrass Control in Corn
  46. Status 56WG
  47. GR-Palmer Amaranth Control in Field Corn May 31, 2007 (38 DAP)
  48. www.gaweed.com



SLIDE CONTENTS
  1. 2008 Corn Weed Control Update Eric P. Prostko Extension Weed Specialist Dept. Crop & Soil Sciences UGA
  2. Herbicide Resistance Concerns for Field Corn glyphosate ALS herbicides Accent, Basis Gold, Beacon, Exceed, Lightning, Option, Permit, Steadfast Atrazine
  3. Glyphosate Resistance Around the World (13 species) rigid ryegrass (1996) goosegrass (1997) horseweed (2000) Italian ryegrass (2001) hairy fleabane (2003) buckhorn plantain (2003) common ragweed (2004) giant ragweed (2004) Palmer amaranth (2005) common waterhemp (2005) johnsongrass (2005) wild poinsettia (2005) johnsongrass (2005) ** Can be found in the US
  4. GA Confirmed Glyphosate-Resistant Palmer Sites 2005 2006 Current Testing 2007
  5. GA Confirmed ALS-Resistant Palmer Sites
  6. Triazine Resistant Palmer Amaranth Macon County - 2007 Atrazine 4L @ 1 qt/A (PRE) fb Atrazine 4L @ 1.5 qt/A + COC @1% v/v (POST) (Photo 14 Days after POST) **15-20 year history of 2-3 atrazine applications/year
  7. Cotton Herbicides/Corn Rotations Staple: 9-10 months Envoke: 210 days Reflex: 10 months Reflex Staple
  8. Burndown Control Options glyphosate paraquat Ignite (glufosinate) tank-mixes with? 2,4-D atrazine others Aim, ET, Harmony Extra (14 DBP), Express (14 DBP), Clarity Need a clean seed-bed at planting
  9. Ryegrass Control - Burndown Hard to kill with 1 shot Ryegrass is most susceptible to glyphosate when applied between boot and early flower stage of growth. Option # 1 Glyphosate @ 1.5 lb ai/A + atrazine 4L @ 3 pts/A Option #2 paraquat @ 0.47 lb ai/A – 2 WBP fb paraquat @ 0.47 lb ai/A + atrazine 4L @ 3 pts/A – at planting RR corn systems Accent???? 1.50 lb ai/A = 35 oz/A of 5.5 lb/gal or 48 oz/A of 4 lb/gal 0.47 lb ai/A = 30 oz/A of 2L or 20 oz/A of 3L
  10. Annual Ryegrass Control with Roundup WM Source: Lins et al. 2007. Weed Technology 21:602-605
  11. Conventional or RR Systems?
  12. Conventional Systems Atrazine still THE major player in any system Prowl in cheap but ……. One of my favorites is Accent + Atrazine If Texas panicum is main problem many Pre-mixes
  13. Why do you not want to spend the money on an Accent + Atrazine treatment in field corn? Data from 21 comparisons from field trials conducted in Georgia from 2001-2007. At $2.00 to $4.00/bu, it only takes a 6 to 13 Bu/A increase to pay for the treatment!!! +59 Bu/A
  14. Corn Yield Response to Various POST Herbicide Treatments Average of 2 tests conducted in 2003 and 2004 (Tifton, Attapulgus) Where Texas panicum is the main weed problem Atrazine PRE @ 1.5 qt/A e d ab a b a a a
  15. Conventional Weed Management Systems Many Pre-Mixes Available Bicep II Magnum (atrazine + Dual II Magnum) Lariat/Bullet (atrazine + Lasso) Lexar (atrazine + Dual Magnum + Callisto) many others preemergence a good choice if many different weed species are present need 0.5” of rainfall or irrigation within 7-10 days for activation
  16. Post-Directed Options for Field Corn Evik Gramoxone Inteon/Firestorm Lorox/Linex Aim tropical spiderwort pigweeds morningglory
  17. U.S. Corn Acres Planted to Herbicide Resistant Hybrids Source: NASS Includes stacked
  18. Should you use the RR corn system? advantages easy Broad spectrum Reduced drift concerns No soil insecticide issues disadvantages No residual over-reliance on a single product Herbicide resistance concerns Volunteer in other RR crops Glyphosate price increases
  19. How would I use RR corn systems? If you are unwilling to use a PRE application of atrazine or something else…. 2 applications of glyphosate 1st application: 21-28 DAP + atrazine (1.5-2.0 qt/A) 2nd application: 35-40 DAP Sequence (s-metolachlor + glyphosate) Expert (s-metolachlor + atrazine + glyphosate) Halex GT (mesotrione + s-metolachlor + glyphosate) Do not forget to include extra seed costs/A in your budgets! Irrigated @ 30,000/A = $6.00/A Dryland @ 18,000/A = $4.00/A
  20. Corn Grain Yield As Influenced by Glyphosate Timing (35 locations) Gower et al., 2003. Weed Technology 17:821-828.
  21. Texas Panicum Control At Harvest with Single or Split Applications of Roundup WM - II CN-04-04 (Attapulgus) Untreated Roundup WM @ 22 ozs/A 21 DAP Roundup WM @ 22 ozs/A 21 + 35 DAP
  22. Corn Yield Response to Single or Split Applications of glyphosate (4.5 lb ae/gal) @ 22 ozs/A. Average of 7 locations (2003-06) DKC67-60RR
  23. Preserving the Value of Glyphosate tank-mix 2,4-D in burndown when glyphosate will be used in-crop or consider paraquat or Ignite if appropriate Alternate glyphosate use with other herbicide modes of action Tank-mix with atrazine Use other practices such as cultivation Do not allow weed escapes to produce seed
  24. New Products that have been tested
  25. Syngenta POST 3 oz/A + COC + UAN or AMS ($12-13/A) Up to 30” tall or 8-leaf corn Palmer amaranth up to 5” If 2,4-D is undesirable or ALS-resistance Tank-mix with atrazine also good on horsenettle Interaction with OP’s Weak on PANTE and CASOB
  26. Texas Panicum Control OR About 30% of the time, Accent has provided better control of Texas panicum But, yields have not been different.
  27. What about Liberty-Link Corn? Glufosinate Liberty (corn) Ignite (cotton) No tech fee up to 24” tall corn or V7 Tank-mix with atrazine Liberty ATZ good on morningglory, Texas millet, sicklepod Hybrid performance??? Garst 8353CB/LL, Hytest 7729Hx/LL, Pioneer 33M57 2008 Rebate Program * Up to $6.25/A
  28. Don’t Forget Liberty-Link Corn! Untreated Liberty 1.67SL @ 32 ozs/A Atrazine @ 90WG @ 1.0 lb/A AMS @ 3 lbs/A Applied 26 DAP CN-10-06 (Croplan Genetics 731 HX/LL) Ponder Farm 52 DAP
  29. Morningglory Control in Corn as much atrazine as possible 1.0 lb/A – PRE fb 1.5 lb/A – POST small grain rotations tank-mix with Aim (POST) 2,4-D, Clarity, Status Liberty-Link Corn Systems split applications of glyphosate (RR corn) * 1st application + atrazine
  30. Pigweed Control in Corn preemergence Atrazine Dual/generics Outlook postemergence Atrazine Accent Callisto 2,4-D Permit Aim glyphosate (RR corn) Status Timing is critical!
  31. Corn Yield Losses Caused by Palmer Amaranth Plants When They Emerge with Crop Massinga et al. 2001. Weed Sci. 49:202-208
  32. This is what a 2” pigweed looks like!!!!
  33. Palmer Amaranth Control in Sorghum-Sudangrass Silage NTC 2,4-D amine @ 1 pt/A (3-4” tall pigweed) (27 DAT) GS-01-07
  34. Palmer Amaranth Control in Field Corn (Photo 14 Days after POST) NTC Roundup WeatherMax @ 22 oz/A Applied EPOST (19 DAT) + POST (37 DAT) CN-01-07
  35. GR-Palmer Amaranth Control in Field Corn May 31, 2007 (38 DAP) NTC Roundup Original Max (22 oz/A) Atrazine (2 qt/A) Prowl H20 (2.1 pt/A) EPOST (18 DAP) CN-07-07
  36. GR-Palmer Amaranth Control in Field Corn May 31, 2007 (38 DAP) NTC Callisto 4SC (3 oz/A) COC (1% v/v) (18 DAP) CN-12-07
  37. GR-Palmer Amaranth Control in Field Corn May 31, 2007 (38 DAP) NTC Halex GT 4.38SC @ 4 pt/A 80/20 @ 0.25% v/v AMS @ 8.5 lbs/100 gals EPOST (18 DAP) CN-07-07
  38. Sicklepod Control in Corn Conventional Systems Atrazine 2,4-D Clarity Status Herbicide-Resistant RR corn system LL corn system
  39. Nutsedge Control not very competitive 800 plants/100 row feet only reduce yields by 2% Eradicane or Sutan - PPI Dual II Magnum or generic – PRE Glyphosate – RR corn Split applications Basagran Permit
  40. Tropical spiderwort (a.k.a. Benghal dayflower) Commelina benghalensis tropical Africa native annual or perennial seeds and rhizomes above and below ground flowers 1,600 seeds/plant alternate host of southern root-knot nematode Reservoir for southern stem blight (white mold)
  41. TSW in Georgia 2004: 29 counties (light blue) 2005: 5 counties (black) 2006: 6 counties (dark blue) 2007: 2 counties (yellow)
  42. TSW Control in Field Corn Depends on planting date 2,4-D or Aim – POST Sequence or Expert in RR corn Aim/Gramoxone/Evik + Dual Magnum – layby Post-harvest may be more important than in-crop Tillage 2 applications of 2,4-D, Gramoxone, or Aim
  43. Post-Harvest Control of Tropical Spiderwort Untreated 2,4-D @ 1.5 pt/A POST1 + POST 2 ($14.41/A) POST1: 8-10” tall COMBE POST2: 2 weeks later Photo 1 week after POST2
  44. Post-Harvest Control of Tropical Spiderwort Untreated Gramoxone Inteon @ 1 qt/A + COC POST1 + POST2 ($25.40/A) POST1: 8-10” tall COMBE POST2: 2 weeks later Photo 1 week after POST2
  45. Johnsongrass Control in Corn Accent no OP soil insecticide hybrid tolerance to Accent hybrid resistance to MDMV Glyphosate in RR corn
  46. Status 56WG BASF dicamba + diflufenzopyr + isoxadifen “Super” Banvel + safener POST 5-10 oz/A ($2.20/oz) broadleaf weed control
  47. GR-Palmer Amaranth Control in Field Corn May 31, 2007 (38 DAP) NTC Status 56WG (5 oz/A) NIS (0.25% v/v) EPOST (18 DAP) CN-07-07
  48. www.gaweed.com