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Weed Control in Field Corn 2025
AUTHOR
Eric P. Prostko
Professor and Extension Weed Specialist
University of Georgia
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TABLE OF CONTENTS
Weed Control in Field Corn 2025
South Georgia Agriculture
Problems
Herbicide Injury or ?????
Glyphosate at Tassel
Volunteer Soybean (RR/Enlist) Control in Field Corn- Roundup + Atrazine + Sandea
Halex GT + Atrazine with Glyphosate-IPA
Halex GT + Atrazine with Different Glyphosate Formulations
Tank-Mixing Order (for most but not all)
Gramoxone Tank-Mixing
Clethodim 2EC @ 3 oz/A Applied the Day of Planting (oops!)
Volunteer/Replant Situations
RR Corn Control (Pioneer 33M57) 40 DAT*
What happens when you spray Liberty on a non-LL corn hybrid?
RR Field Corn (DKC-6835) Control for Replant - 2024
Field Corn Yield Loss (%) Caused by Uncontrolled Weeds in UGA Weed Science Research Trials (2007-2024)
As always...
Field Corn Weed Control Programs
EPA Updates Atrazine CE-LOC to 9.7 µg/L (up from 3.4 µg/L) - July 8, 2024
New(er) Products Being Tested - I Not in UGA Pest Control Handbook (yet?)
New(er) Products Being Tested - II Not in UGA Pest Control Handbook (yet?)
Roundup + Liberty Rates?
Weed Control In Field Corn with Roundup + Liberty - 2024
Liberty® ULTRA 1.76SL
Conventional Field Corn
Weed Control in Field Corn with No Roundup, Liberty, or Atrazine - 2024
GR-Resistant Ryegrass?
Burndown Control of Wheat/Ryegrass - 2024
Annual Ryegrass Control with Roundup WeatherMax 5.5SL
Burndown Control of Wheat/Ryegrass - 2024
Pre-Plant Burndowns
Post-Harvest Benghal Dayflower Test - 2024
Post-Harvest Tropical Spiderwort Control
Post-Harvest Tropical Spiderwort Control
A Must Have for GA Growers?
Are you satisfied with your weed control? Do you want/need better spray coverage?
Questions/Comments
SLIDE CONTENTS
Weed Control in Field Corn 2025 Eric P. Prostko Extension Weed Specialist Dept. Crop & Soil Sciences
South Georgia Agriculture Tifton Coastal Plain Soils, high rainfall (47”/year), supplemental irrigation, soils never freeze, crop diversity (peanut, cotton, soybean, corn, pecans, watermelons, onions, blueberries, cantaloupes, peppers, tomatoes, collards, broccoli, peaches)
Problems
Herbicide Injury or ????? After 30 lbs S Before T. Price April 2024
Glyphosate at Tassel Honcho K6 5.5SL @ 40 oz/A + Atrazine 4L @ 16 oz/A; P-1847, DKC-7045 C. Cloud 06/14/24 https://www.pioneer.com/CMRoot/Pioneer/US/Non_Searchable/agronomy/cropfocus_pdf/off_label_glyphosate_app_corn.pdf
Volunteer Soybean (RR/Enlist) Control in Field Corn Roundup + Atrazine + Sandea R. Ethredge April 8 6 DAT
Halex GT + Atrazine with Glyphosate-IPA Macon Co. April 16, 2024
Halex GT + Atrazine with Different Glyphosate Formulations April 17, 2024 ~24 Hours after mixing Roundup PowerMax3 (K-salt) Credit Extreme (IPA + K-salt) GlySupreme Extra (IPA)
Tank-Mixing Order (for most but not all)
Gramoxone Tank-Mixing
Clethodim 2EC @ 3 oz/A Applied the Day of Planting (oops!) Macon Co. April 22, 2024
Volunteer/Replant Situations most hybrids are RR or RR + LL Options Gramoxone (paraquat) + PSII Inhibitor (Atrazine or Metribuzin)???? Liberty (glufosinate) Select (clethodim) 6 day plant-back corn growing point below ground until ~V5 stage
RR Corn Control (Pioneer 33M57) 40 DAT* NTC (123 Bu/A) SelectMax 0.97EC @ 6 oz/A Induce @ 0.25% v/v AMS X-TRA @ 2.5% v/v (0 Bu/A) Gramoxone Inteon 2SL @ 40 oz/A Atrazine 4L @ 32 oz/A Agridex @ 1% v/v (27 Bu/A) *Applied to 7” tall corn, V4 stage of growth
What happens when you spray Liberty on a non-LL corn hybrid? CN-01B-16 DKC 66-59 Liberty @ 29 oz/A + Atrazine @ 48 oz/A Applied V4-V5 (6”) *Only made 28 Bu/A!!!!! *Other treatments made ~231 Bu/A *88% yield loss 6 DAT 15 DAT
RR Field Corn (DKC-6835) Control for Replant – 2024 Applied 20 DAP (V5, 11” tall) CN-08-24 June 7 23 DAT NTC Select Max 0.97EC @ 6 oz/A Induce @ 0.25% v/v Gramoxone 3SL @ 32 oz/A Induce @ 0.25% v/v Liberty 2.34SL @ 32 oz/A AMSOL @ 2% v/v
Field Corn Yield Loss (%) Caused by Uncontrolled Weeds in UGA Weed Science Research Trials (2007-2024) Treated vs. Non-treated 200 Bu/A X 0.33 X $4.10 = $271/A 250 Bu/A X 0.33 X $4.10 = $338/A What about harvest? What about next year?
As always……… start clean cover crops, tillage, herbicides multiple residuals Timely POST’s Post-Harvest “The Greatest American County Agent”
Field Corn Weed Control Programs
EPA Updates Atrazine CE-LOC to 9.7 µg/L (up from 3.4 µg/L) - July 8, 2024 CE-LOC = concentration-equivalent level of concern HUC = hydrologic unit code 2026? Worth/Turner Tattnall/Evans Watersheds with higher predicted atrazine concentration are expected to have waterbodies with greater vulnerability to atrazine runoff due to landscape features (e.g., soil restrictive layers), precipitation, and atrazine usage.
New(er) Products Being Tested - I Not in UGA Pest Control Handbook (yet?) AMVAC Sinate (glufosinate + topramezone) Impact Core (topramezone + acetochlor) BASF Surtain (pyroxasulfone + saflufenacil) Bayer TriVolt (isoxaflutole + thiencarbazone + flufenacet) Corteva Kyro (encapsulated acetochlor + topramezone + clopyralid) Resicore (mesotrione + acetochlor + clopyralid) Resicore XL (mesotrione + encapsulated acetochlor + clopyralid) Syngenta Acuron GT (bicyclopyrone + s-metolachlor + mesotrione + glyphosate) Acuron XR (bicyclopyrone + s-metolachlor + mesotrione + atrazine) Storen (s-metolachlor + mesotrione + bicyclopyrone + pyroxasulfone)
New(er) Products Being Tested - II Not in UGA Pest Control Handbook (yet?) Helm Katagon (tolpyralate + nicosulfuron) Helmet Maxx (metolachlor + atrazine + mesotrione) Helena Empyros (tolpyralate + s-metolachlor) Empyros Triad (tolpyralate + s-metolachlor + atrazine) Empyros Triad Flex (tolpyralate + s-metolachlor + atrazine) Valent Maverick (mesotrione + pyroxasulfone + clopyralid) Summit Agro Restraint (tolpyralate + acetochlor + dichlormid)
Roundup + Liberty Rates?
Weed Control In Field Corn with Roundup + Liberty - 2024 CN-07-24 May 15 20 DAT NTC Roundup P-Max3 5.88SL @ 22 oz/A Liberty 2.34SL @ 22 oz/A Aatrex 4L @ 64 oz/A Prowl H2O 3.8SC @ 32 oz/A Applied POST (24 DAP) Roundup P-Max3 5.88SL @ 27 oz/A Liberty 2.34SL @ 27 oz/A Aatrex 4L @ 64 oz/A Prowl H2O 3.8SC @ 32 oz/A Applied POST (24 DAP) Roundup P-Max3 5.88SL @ 32 oz/A Liberty 2.34SL @ 32 oz/A Aatrex 4L @ 64 oz/A Prowl H2O 3.8SC @ 32 oz/A Applied POST (24 DAP)
Liberty® ULTRA 1.76SL BASF glufosinate-P-ammonium More active isomer Dual vs. Dual Magnum Metolachlor vs. S-metolachlor lower use rate (19-29 oz/A) Mandatory downwind spray buffer ground = 10’/aerial = 50’ 3 points for ESA runoff/erosion Tift Co. = 2 points sandy soils = 2 points
Conventional Field Corn Dual, Warrant, Outlook (PRE) Callisto, Laudis, Shieldex, Revulin Q, Steadfast Q (POST) + Atrazine (64 oz/A) + Prowl (32 oz/A) Anthem Maxx, Dual, Warrant, Outlook, Zidua if you don’t like/want/Prowl but……….. adjuvant as needed/required
Weed Control in Field Corn with No Roundup, Liberty, or Atrazine - 2024 CN-01-24 May 23 52 DAP Dual II Magnum 7.62EC @ 16 oz/A PRE Callisto 4SC @ 3 oz/A Prowl H20 3.8SC @ 32 oz/A Induce @ 0.25% v/v POST (28 DAP) NTC Dual II Magnum 7.62EC @ 16 oz/A PRE Laudis 3.5SC @ 3 oz/A Prowl H20 3.8SC @ 32 oz/A Induce @ 0.25% v/v POST (28 DAP) Dual II Magnum 7.62EC @ 16 oz/A PRE Impact 2.8SC @ 1.25 oz/A Prowl H20 3.8SC @ 32 oz/A Induce @ 0.25% v/v POST (28 DAP) Dual II Magnum 7.62EC @ 16 oz/A PRE Shieldex 3.33SC @ 1.35 oz/A Prowl H20 3.8SC @ 32 oz/A Induce @ 0.25% v/v POST (28 DAP)
GR-Resistant Ryegrass? Grady Co. March 13, 2024
Burndown Control of Wheat/Ryegrass - 2024 BN-01-24 March 13 22 DAT NTC Roundup PowerMax3 5.55SL @ 25 oz/A AMSOL @ 2% v/v
Annual Ryegrass Control with Roundup WeatherMax 5.5SL Source: Lins et al. 2007. Weed Technology 21:602-605
Burndown Control of Wheat/Ryegrass - 2024 BN-01-24 March 13 22 DAT NTC Gramoxone 3SL @ 32 oz/A Aatrex 4L @ 32 oz/A Induce @0.25% v/v
Pre-Plant Burndowns CN-02-24 April 10 20 DAT NTC Helmquat 3SL @ 32 oz/A Aatrex 4L @ 32 oz/A Induce @ 0.25% v/v
Post-Harvest Benghal Dayflower Test - 2024 Grady Co. 09/10/24
Post-Harvest Tropical Spiderwort Control – 2024 COMBE: 12-16” tall; flowering; POST1 = 09/10/24; POST2= 09/17/24 PH-01A-24 October 2 15 DAT (POST2) NTC Gramoxone 3SL @ 32 oz/A Induce @ 0.25% v/v POST1 + POST2 Roundup P-MAX3 5.88 SL @ 32 oz/A Enlist One 3.8SL @ 24 oz/A POST1 + POST2
Post-Harvest Tropical Spiderwort Control – 2024 COMBE: 12-16” tall; flowering; POST1 = 09/10/24; POST2= 09/17/24 PH-01A-24 October 2 15 DAT (POST2) NTC Roundup P-MAX3 5.88 SL @ 32 oz/A Aim 2EC @ 1.5 oz/A POST1 + POST2 Roundup P-MAX3 5.88 SL @ 32 oz/A Reviton 2.83SC @ 1.5 oz/A POST1 + POST2
A Must Have for GA Growers?
Are you satisfied with your weed control? Do you want/need better spray coverage? Think about …… tractor speed boom height water volume droplet size
Questions/Comments