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Basic Field Corn Weed Management for New Extension Agents - 2013
AUTHOR
Eric P. Prostko
Professor and Extension Weed Specialist
University of Georgia
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TABLE OF CONTENTS
Basic Field Corn Weed Management for New Extension Agents - 2013
Cultural Practices
Mechanical Cultivation
Insecticide/Herbicide Interactions
Guidelines for Herbicide Use with Counter
Field Corn (DKC 66-97) Yield Response to Counter fb Steadfast - 2012
Corn Hybrid/Herbicide Interactions
DKC-6469 Response to Steadfast Q
DKC 64-69 Yield Response to POST Applications of Steadfast Q
Hybrid/Herbicide Interactions
Hybrid/Herbicide Interactions - Online Updates
Weed/Disease Interactions
Corn Stages of Growth
Know Your Grasses
Texas Panicum vs. Crabgrass
Oldies But Goodies
Atrazine Use in Field Corn
Atrazine Issues
2011 Enhanced Atrazine Degradation Project
Atrazine Half Lives (T1/2) from Georgia Soil Samples - 2011
2007, 2008, 2010 Macon County Triazine-Resistance Survey
Prowl Use in Field Corn
Optimum Prowl/Pendimax Timing- Field Corn
Prowl Injury In Field Corn
Current GA Field Corn Weed Control
The Power of a PRE Herbicide
Weed Control in Field Corn - 2013
Weed Control in Field Corn with Steadfast Q - 2013
Weed Control in Field Corn with Halex GT - 2013
Post-Directed Options for Field Corn
Post-Harvest Palmer Amaranth Populations Must be Managed!
Post-Harvest (Corn) Pigweed Problems
Morningglory Control in Corn
Nutsedge Control
TSW Control in Field Corn
Reduced Tillage Systems
Burndown Control Options
Ryegrass Control
Where to go for more information?
SLIDE CONTENTS
Eric P. Prostko, Ph.D. Professor and Extension Weed Specialist Dept. Crop & Soil Sciences Basic Field Corn Weed Management For New Extension Agents - 2013
Cultural Practices Planting Date Row Spacing Fertility Irrigation give the crop a competitive edge against weeds
Mechanical Cultivation Time Diesel fuel prices Strip-tillage no weeds are steel-resistant!!!
Insecticide/Herbicide Interactions Insecticides Organophosphates (OPS) Counter, Lorsban, Thimet Herbicides Steadfast Q Capreno Halex GT Sandea Why? overload the plants ability to metabolize chemicals
Field Corn (DKC 66-97) Yield Response to Counter fb Steadfast - 2012 CN-06-12 Bu/A Treatment LSD 0.10 = 26
Corn Hybrid/Herbicide Interactions some corn hybrids are sensitive to certain herbicides Companies screen for tolerance to . Amides (Dual) Benzoic Acid/phenoxy (dicamba) HPPD (Calliso/Balance) SU (Steadfast) DuPont Q Products Steadfast Q, Resolve Q Isoxadifen (safener)
DKC-6469 Response to Steadfast Q CN-18-13 May 3 16 DAT Roundup WeatherMax @ 22 oz/A Aatrex @ 64 oz/A Roundup WeatherMax @ 22 oz/A Steadfast Q @ 1.5 oz/A Aatrex @ 64 oz/A Roundup WeatherMax @ 22 oz/A Steadfast Q @ 3.0 oz/A Aatrex @ 64 oz/A
DKC 64-69 Yield Response to POST Applications of Steadfast Q (RUWM @ 22 oz/A, ATZ @ 64 oz/A, STDQ @ 1.5 or 3 oz/A) P = 0.5017 CV = 1.75 Applied 28 DAP V4, 6 tall corn Bu/A
Hybrid/Herbicide Interactions Check Pioneer and Dekalb Web-sites in spring for new listing of hybrid/herbicide interactions.
Weed/Disease Interactions Maize Dwarf Mosaic Virus (MDMV) Maize Chlorotic Dwarf Virus (MCDV) johnsongrass aphid/leafhoppers hybrid tolerance
Corn Stages of Growth All leaves and ear shoots are initiated at V3 stage and completed by V5
Know Your Grasses large crabgrass johnsongrass fall panicum broadleaf signalgrass Source: SWSS Weed ID Guide
Texas Panicum vs. Crabgrass WSSA Fringe of hairs membranous Texas panicum Southern crabgrass
Oldies But Goodies Atrazine Prowl (pendimethalin)
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 Rainfall soil type Enhanced degradation
Atrazine Issues Resistance Enhanced degradation Environmental Concerns? www.atrazinefacts.com Source: USGS Pesticide National Synthesis Project
2011 Enhanced Atrazine Degradation Project 20 soil samples collected from Georgia corn fields in August Burke Co. Decatur Co. Jefferson Co. Mitchell Co. Macon Co. Seminole Co. Worth Co. (control) #11 UGA-Ponder Farm No atrazine for 12+ years
Atrazine Half Lives (T1/2) from Georgia Soil Samples - 2011 Sample T1/2(days)
2007, 2008, 2010 Macon County Triazine-Resistance Survey
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
Optimum Prowl/Pendimax Timing Field Corn Prowl will not control emerged grasses!!!
Prowl Injury In Field Corn Prowl Control
Current GA Field Corn Weed Control For most in GA . Atrazine + Glyphosate (RR corn) Liberty (LL corn) Steadfast Q Laudis or Capreno Halex GT (glyphosate + Callisto + Dual) If I was King, I would make every GA grower use 1 qt/A Atrazine PRE fb 1.5 qt/A + 1 of the above!
The Power of a PRE Herbicide CN-13-12 April 24 28 DAT NTC Dual II Magnum 7.64EC 1 pt/A (PRE) Atrazine 4L 1 qt/A (PRE)
Weed Control in Field Corn 2013 CN-15-13 May 28 69 DAP NTC Aatrex 4L @ 32 oz/A (PRE) Roundup W-Max @ 22 oz/A (POST) Aatrex 4L @ 48 oz/A (POST) Aatrex 4L @ 32 oz/A (PRE) Liberty 2.34 SL @ 29 oz/A (POST) Aatrex 4L @ 48 oz/A (POST)
Weed Control in Field Corn with Steadfast Q - 2013 CN-13-13 May 23 30 DAT NTC Steadfast Q @ 1.5 oz/A Aatrex @ 64 oz/A COC @ 1% v/v
Weed Control in Field Corn with Halex GT 2013 CN-09-13 MAY 31 NTC Halex GT @ 58 oz/A Aatrex @ 32 oz/A NIS @ 0.25% v/v AMS Xtra @ 2.5% v/v Applied April 9 (20 DAP)
Post-Directed Options for Field Corn Evik Gramoxone/Firestorm (paraquat) Lorox/Linex Aim tropical spiderwort pigweeds Morningglory (Ipomoea sp.)
Post-Harvest Palmer Amaranth Populations Must be Managed!
Post-Harvest (Corn) Pigweed Problems Decreasing daylight hastens flower and seed production Flowering (3-4 weeks) Seed production (2-3 weeks) Some germination at 410F (8%) Control Options Mowing/Tillage (>6 weeds) Herbicides (<6 weeds) No small grain Gramoxone + Dual Magnum or Warrant (?) Small Grain planted soon Gramoxone + 2,4-D or dicamba When can we stop worrying about seed production? Keeley et al. 1987. Weed Science 35:199-204 Steckel et al., 2004. Weed Science 52:217-221
Morningglory Control in Corn as much atrazine as possible 1.0 lb/A PRE fb 1.5 lb/A POST small grain rotations 2,4-D, Clarity, Status, Aim, ET Liberty-Linkฎ Corn Systems split applications of glyphosate (RR corn) * 1st application + atrazine Evik (PDIR) Harvest Aids Aim Early-harvest
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 Sandea
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
Reduced Tillage Systems
Burndown Control Options glyphosate Paraquat Liberty (glufosinate) tank-mixes with? 2,4-D, dicamba atrazine Leadoff Aim, ET Need a clean seed-bed at planting
Ryegrass Control Glyphosate-resistant or not? Fall (mid-October Mid-November) Tillage (double disk) or Dual Magnum @ 1.33 pt/A Mid-January Mid-February 2 - 6 tall Select Max @ 12-16 oz/A or Clethodim 2EC @ 6-8 oz/A Corn 30 days Nighttime temps > 470 F March 1-20 Gramoxone 2SL @ 3-4 pt/A May need 2 applications (10-14 days apart) + atrazine @ 1 qt/A (corn) Source: Drs. Jason Bond and Tom Eubank, MS State University
Where to go for more information? UGA Weed Science Web-Site www.gaweed.com UGA Pest Control Handbook UGA Corn Production Guide Call me at any time!!! 229-392-1034