Strategies for Managing Herbicide

Resistant Palmer Amaranth in

Soybean - 2012

Eric P. Prostko

Professor and Extension Weed Specialist

Dept. Crop & Soil Sciences

Herbicide-Resistant Palmer Amaranth in GA ALS (2000)

Glyphosate (2005)

Atrazine (2009)

ALS + GLY (2009)

DNA + ALS + GLY (2010)

ALS + GLY + ATZ (2011)

Important Things We Know About Palmer Amaranth

• Well-adapted to Georgia!– Native to Sonoran desert

• Separate male and female plants• Lots of seed!!!!

– 400,000 – 500,000/female plant

• Seed do not last long in soil– 20% germ after 30 months

• Seed do not emerge from deep depths (≥ 3-4”)

• Seed need light to germinate• Resistance trait moves in pollen

– At least 1000 feet!!

Palmer AmaranthVery ompetitive

• 1 Palmer amaranth plant per meter (3.3 ft) of row can reduce soybean yield by 32%.

Pigweed Control is not impossible!!!!

Common Reasons for Failure:1) did not start clean2) did not use a residual3) residual did not get activated4) POST applications are too late5) short arms and deep pockets

Many pigweed problems are due to weeds already up at planting!

Palmer Amaranth Growth 22 days after starting clean

June 22, 2011Attapulgus, GA

Dryland Production SystemsA Difficult Challenge!

• Growers need to think about mechanical herbicide incorporation

• Will help but not a guarantee

• Success will depend upon……

– operator

– implement

– soil conditions

Tillage and Pigweed

Bottom PlowBottom Plow Chisel PlowChisel Plow

Source: Twiggs Co., April 22, 2010Source: Twiggs Co., April 22, 2010

Extreme Cover Crops

11 22

33 44

Row Spacing

Washington County 2009

Irrigation

Herbicides for Pigweed Control in Soybeans

• Residual Herbicides– Authority MTZ, Authority XL,

Canopy/Cloak, Boundary, Valor, Valor XLT, Prefix, Dual Magnum/Generics, Tricor, Prowl, Intrro, Treflan, Envive, Warrant

• Postemergence– Reflex/Dawn, Prefix, Cobra,

Ultra Blazer, Flexstar GT, Harmony (ALS?), Ignite (LL soybeans)

2012 Monsanto Incentives Program

Consider metribuzin on soybean?

• Not a PPO• Not a PPO• Good on pigweed• Can be applied PPI• Issues

– soil texture, OM, pH– Varieties– Rotations– Company support– Lack of incentive at dealer

level– Cost/A

TriCor 75DFTriCor 75DF

Metribuzin 75DFMetribuzin 75DF

Metribuzin Injury

Palmer Amaranth Control in Soybeans - 2011

SB-13-2011June 23, 201130 DAP

NTC Valor SX 51WG @ 2 oz/A

Palmer Amaranth Control in Soybeans - 2011

SB-13-2011June 23, 201130 DAP

NTC Boundary 6.5EC @ 1.5 pt/A

Liberty-Link Soybeans - 2011

NTCNTC Prefix @ 2.5 pt/A (PRE)Ignite @ 29 oz/A (MPOST)

AMS Xtra @ 2.5% v/v (MPOST)

Ignite @ 29 oz/A (EPOST)Warrant @ 3 pt/A (EPOST)

AMS Xtra @ 2.5% v/v (EPOST)

SB-04-11July 2058 DAP

This is what a 2” pigweed looks like!!!!

On the HorizonOn the Horizon

• Zidua

• Anthem

• Fierce

• Enlist Soybean – Enhanced tolerance to 2,4-D– Stacked with glyphosate– 2015?

• Dicamba Resistant Soybeans– Monsanto/BASF– Stacked with glyphosate– 2013?

• Zidua 85WG

• Pyroxasulfone

• Residual control of annual grasses and certain broadleaf weeds including pigweed

• Same MOA as Dual or Warrant but used at lower rates

• Use rate: 1-2 oz/A

Palmer Amaranth Control in Soybeans - 2011

SB-13-2011June 23, 201130 DAP

NTC Zidua 85WG @ 2 oz/A

- Fierce 76WDG

- February 2012 (?)

- Valor (33.5%) + Pyroxasulfone (42.5%)

- preplant or preemergence

- 3 oz/A on coarse soils (Valor @ 2 oz/A + Pyrox @ 1.5 oz/A)

Palmer Amaranth Control with Fierce

NTCNTC Fierce 76WG @ 3 oz/AFierce 76WG @ 3 oz/A

SB-14-10SB-14-10July 22, 2010July 22, 201050 DAT50 DAT

• Anthem 2.15L

• Cadet (0.0632 lb/gal) + Pyroxasulfone (2.0868 lb/gal)

• Residual control of annual grasses and certain broadleaf weeds including pigweed

• Use rate: 3.5-7.0 oz/A (?)

Weed Control in Soybeans with Anthem

SB-18-11June 2465 DAP

NTC Anthem 2.15SL @ 8 oz/A – PRERoundup W-Max 5.5SL @ 22 oz/A - POST

Enlist™ Herbicide Tolerant Enlist™ Herbicide Tolerant SoybeanSoybean

• tolerance to 2,4-D + glyphosate + glufosinate (Ignite)

• Colex-D™ technology– 2,4-D choline– lower volatility– lower drift potential– enhanced handling/mixing

characteristics– reduced odor

• 1 Burndown/PRE application + 2 POST applications (R2 stage)

• Enlist™ Duo– DMA-Glyphosate (1.71 lb ae/gal) + 2,4-

D choline (1.63 lb ae/gal)– 3.5 pt/A

• 2015 Product Launch

Enlist Soybeans – 2010 (GA)

SB-09-10June 28

NTC Ignite 280 2.34SL @ 22 oz/AWeedar 64 4SL @ 17 oz/AN-Pack AMS @ 2.5% v/v

Applied May 28 and June 18

PPO Herbicide ResistanceThey must be protected!!!!

• Resistance has already been reported in other areas!!!

• Amaranthus quitensis– 2005 (Bolivia)

• Common waterhemp– 2001 (Kansas)– 2002 (Illinois)– 2005 (Missouri)– 2009 (Iowa)

• Common ragweed– 2005 (Delaware)– 2006 (Ohio)

• Wild poinsettia– 2004 (Brazil)

Final Thoughts

• Know your enemy• Start Clean• Tillage and/or Cover

Crops• Narrower Row Spacing• Residual herbicides (2)• Reward Programs• Timely POST’s• Irrigation system?????• Roque Escapes

For More Weed Science Info

www.gaweed.com