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Corn Weed Management for “New” County Extension Agents

Corn Weed Management for “New” County Extension Agents. Eric P. Prostko Extension Weed Specialist Department of Crop & Soil Sciences - UGA. April 2007. Cultural Practices. Planting Date Row Spacing Fertility give the crop a competitive edge against weeds. Mechanical Cultivation. Time

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Corn Weed Management for “New” County Extension Agents

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  1. Corn Weed Management for “New” County Extension Agents Eric P. Prostko Extension Weed Specialist Department of Crop & Soil Sciences - UGA April 2007

  2. Cultural Practices • Planting Date • Row Spacing • Fertility • give the crop a competitive edge against weeds

  3. Mechanical Cultivation • Time • Diesel fuel prices • Strip-tillage

  4. Insecticide/Herbicide Interactions • Insecticides • Organophosphates (OP’S) • Counter, Lorsban, Thimet • Herbicides • Accent, Beacon, Option, Callisto, Steadfast, Basis

  5. Weed/Disease Interactions • Maize Dwarf Mosaic Virus (MDMV) • Maize Chlorotic Dwarf Virus (MCDV) • johnsongrass • aphid/leafhoppers • Accent/Beacon • hybrid tolerance

  6. Corn Stages of Growth

  7. Specific Herbicides • Atrazine • Prowl • Accent

  8. Atrazine Use in Field Corn • Since 1958 • foundation • inexpensive • excellent crop tolerance • PPI, PRE, POST (12”) • broad-spectrum • up to 2.5 lb ai/A/year • easily tank-mixed • weak on T. panicum • does not last full season in SE

  9. Conventional Weed Management SystemsMany 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

  10. Prowl Use in Field Corn • since 1975 • pendimethalin • DNA or “yellow” • inexpensive but…. • do not apply PRE • early-post (EPOST) • up to 30” tall or V8 • crop injury concerns • Planting depth (1.5”) • Furrow closure

  11. Optimum Prowl/Pendimax Timing Field Corn Prowl will not control emerged grasses!!!

  12. Prowl Injury In Field Corn Prowl Control

  13. Accent Use in Field Corn • since 1991 • nicosulfuron • sulfonylurea • ALS-inhibitor • POST • up to 20” tall or V6 • 20-36” (PDIR) • Pigweed, Texas panicum • Weak on crabgrass • Hybrid sensitivity • OP interaction • Tank-mix with atrazine • cost

  14. Corn Hybrid/Herbicide Tolerance • Pioneer • http://www.pioneer.com/CMRoot/Pioneer/usa/agronomy/corn/herb_table.pdf

  15. Why do you not want to spend the money on an Accent + Atrazine treatment in field corn? Data from 18 irrigated weed control trials conducted in Georgia from 2001-2006. At $2.00 to 3.00/bu, it only takes a 9 to 14 bu/A increase to pay for the treatment!!!

  16. Know Your Grasses broadleaf signalgrass large crabgrass johnsongrass fall panicum Source: SWSS Weed ID Guide

  17. Texas Panicum vs. Crabgrass Fringe of hairs membranous WSSA Southern crabgrass Texas panicum

  18. Post-Directed Applications

  19. Post-Directed Options for Field Corn • Evik • Gramoxone Inteon/Firestorm (paraquat) • Lorox/Linex • Aim • tropical spiderwort • pigweeds • morningglory

  20. Herbicide Resistant Corn Technologies

  21. Should you use the RR corn system? • advantages • Inexpensive • 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

  22. 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) • Do not forget to include extra seed costs/A in your budgets! • Irrigated @ 30,000/A = $12-13.00/A • Dryland @ 18,000/A = $7-8.00/A

  23. Texas Panicum Control At Harvest with Single or Split Applications of Roundup WM - II Untreated Roundup WM @ 22 ozs/A 21 + 35 DAP Roundup WM @ 22 ozs/A 21 DAP CN-04-04 (Attapulgus)

  24. 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

  25. 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 2007 Rebate Program * Buy 20 gals and get a $5-6/A rebate

  26. Don’t Forget Liberty-Link Corn! 83 Bu/A 114 Bu/A 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

  27. Clearfield Corn Systems • Not used that much or at all in Georgia • Pursuit • Lightning • Pursuit + Arsenal • POST • Non-GMO • ALS-resistance

  28. Common Weed Problems • Texas panicum (Texas millet, buffalograss) • sicklepod (coffeeweed) • pigweeds • morningglories • nutsedges • johnsongrass • Tropical spiderwort (Benghal dayflower)

  29. Texas Panicum Control in CornWhat works! • Prowl/Pendimax (DPRE/EPOST) • Accent (POST) • Option (POST) • RR or LL system • post-directed * Evik/Paraquat

  30. Texas Panicum Control OR • About 30% of the time, Accent has provided better control of Texas panicum • But, yields have not been different.

  31. Texas Panicum Control (104 DAT) - IIAccent vs Option - 2004 Untreated Accent @ 0.67 ozs/A Agrioil @ 1% v/v Option @ 1.5 ozs/A MSO @ 1.25% v/v AMS @ 3 lbs/A CN-04-04 (Attapulgus) Applied 21 DAP PANTE = 1-2”, 2-4 leaf

  32. Sicklepod Control in Corn • Conventional Systems • Atrazine • 2,4-D • Clarity • Herbicide-Resistant • RR corn system • LL corn system

  33. Pigweed Control in Corn • preemergence • Atrazine • Dual/generics • Outlook • postemergence • Atrazine • Accent • Callisto • 2,4-D • Permit • Aim • glyphosate (RR corn) • Timing is critical!

  34. 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 • Harvest Aids • 2,4-D, sodium chlorate, glyphosate, Aim, paraquat

  35. 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

  36. Johnsongrass Control in Corn • Accent • no OP soil insecticide • hybrid tolerance to Accent • hybrid resistance to MDMV • Glyphosate in RR corn

  37. 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)

  38. TSW in Georgia * confirmed in 29 counties by GA Dept. of Ag and UGA in 2004(light blue) * identified in 4 more counties in 2005(black) *identified in 6 more counties in 2006 (dark blue)

  39. 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

  40. Reduced Tillage Systems

  41. Burndown Control Options • glyphosate • Paraquat • Ignite (glufosinate) • tank-mixes with? • 2,4-D • atrazine • Need a clean seed-bed at planting

  42. Ryegrass Control - Burndown • Hard to kill with 1 shot • Option # 1 • Glyphosate @ 1.125 lb ae/A + atrazine @ 3 pts/A • Option #2 • Gramoxone Inteon @ 1.9 pts/A – 2 WBP fb Gramoxone Inteon @ 1.9 pts/A + atrazine @ 3 pts/A - planting • RR corn systems • Accent????

  43. Herbicide-Resistant Weed Issues • Glyphosate • ALS

  44. Herbicide ResistanceDefinition • inherited ability of a weed or crop biotype to survive a herbicide application to which the original population was susceptible. Biotype = a group of plants within a species that has biological traits that are not common to the population as a whole.

  45. Glyphosate Resistance Around the World (12 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) ** Can be found in the US

  46. ** 3/15/2007

  47. What does ALS mean? • Acetolactate synthase (ALS) • Acetohydroxyacid synthase (AHAS) • chloroplast enzyme needed to form certain amino acids • Valine, leucine, isoleucine • Herbicide families • Imidazolinones • Sulfonylureas • Sulfonanalides • benzoates

  48. Accent Ally/Cimarron Beacon Beyond Cadre Classic Envoke Exceed Express Finesse FirstRate Glean Harmony Extra Maverick Pro Osprey Peak Permit Pursuit Python Scepter Staple Strongarm Commonly Used ALS Herbicides

  49. ALS-Resistant Palmer Amaranth Survey

  50. Where to go for more information? • UGA Weed Science Web-Site • www.gaweed.com • UGA Pest Control Handbook • UGA Corn Production Guide

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