Managing ALS-Resistant Palmer Amaranth in Peanuts Eric P. Prostko Extension Weed Specialist Department of Crop & Soil Sciences The University of Georgia

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

Commonly Used ALS Herbicides 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

Managing ALS-Resistant Palmer Amaranth in Peanuts Weed-free at planting Preemergence herbicides Prowl or Sonalan on every acre + ? Postemergence herbicides Cultivation Harvest Aids Rope-wick applications Mowing Other tactics Crop rotation with corn (atrazine)

Preemergence Herbicides Valor Dual Magnum Generic Metolachlors Outlook/Propel What about….. Reflex Goal Solicam activation

Metolachlor Mysteries

GR-Pigweed/Soybean Test – II (2006) 7 WAP RUWM (POST) Valor @ 2 oz/A (PRE) RUWM (POST) Untreated

Valor in Peanuts - The Bottom Line Plant at least 1.5” deep and apply within 2 days of planting Injury will occur if heavy rainfall occurs from cracking until ~2 WAC peanut yield should not be reduced if stand is not lost hose and nozzle clean-out very important!!!!! except this or do not use it Glyphosate was developed as an industrial cleaner!!

Valor Injury in Peanut

Postemergence Herbicides Timing, timing, timing 16” in 1 week Paraquat G-Inteon Firestorm 15 GPA flat fan nozzles tractor speed Cobra Ultra Blazer Storm 2,4-DB Cobra, Storm, Ultra Blazer, Valor have the same mode of action (PPO inhibitors)

How/Why do we let pigweeds get this big????

Will these herbicides control large pigweeds?

Cobra 2EC @ 12.5 ozs/A + COC @ 1% v/v applied to 17” tall pigweed 4 DAT 1 DAT 7 DAT 16 DAT

2,4-DB/Cobra Test – 2006 Untreated Cobra 2EC @ 12.5 oz/A Agrioil @ 1% v/v POST 2,4-DB 1.75SL @ 1.1 pt/A + Agrioil @ 1% v/v (POST) fb Cobra 2EC @ 12.5 oz/A Agrioil @ 1% v/v POST2 POST: June 5 (17” tall pigweed) POST2: June 9 Photos taken 24 days after POST application

Does Cobra reduce yields??

Peanut (GA Green) Response to Cobra 78 DAP - 2006 3556 lbs/A – Tifton 4450 lbs/A - Plains 4003 lbs/A – Tifton 4319 lbs/A - Plains Untreated Cobra @ 12.5 ozs/A Agrioil @ 1% v/v Applied 30 DAP

PPO Resistance??? PPO or Protox Protoporphyrinogen oxidase Enzyme found in chloroplast and mitochondria 3 species worldwide Common waterhemp Kansas (2001) Illinois (2002) Common ragweed Delaware (2005) Wild poinsettia Brazil (2004)\ Ultra Blazer, Cobra, Goal, Reflex, Ronstar, Resource, Aim, Valor, Storm, Spartan

Where do Cadre and Strongarm fit in? Effective on many other weeds Cadre is the only herbicide that will control purple nutsedge

Cadre @ 4 ozs/A + 2,4-DB @ 1.1 pt/A + COC @ 1% v/v – 34 DAT Applied to 17” tall pigweed

Cultivation (no weeds are steel-resistant!!!) Time Diesel fuel prices Strip-tillage Twin rows White mold

Rope-wick Applicators glyphosate is labeled for wiper applications in row middles 33-50% solution Opposite directions 5 MPH or less GR-pigweed concerns??

Mowing Weed/peanut height differential Digging and harvest aid Flail mower better than rotary mower diesel fuel prices Time???

What if we do not control Palmer amaranth? Crop (State) Density Yield Loss Source Corn (KS) 0.5-8 plants/m 11-91% Weed Sci. 2001 49:202-208 Soybean (AK) 0.33-10 plants/m 17-68% 1994 42:523-527 Grain sorghum (OK) 1-18 plants/15 m 4-63% Weed Tech. 2004 18:23-29 Peanut (NC) 1-5 plants/m 28-66% Burke and Wilcut (in-press) Cotton (TX) 1-10 plants/9.1 m 13-54% 15:408-412

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