2007 Peanut Weed Management Update for County Agents Eric P. Prostko Extension Weed Specialist Department of Crop & Soil Sciences The University of Georgia Extension Agent Training – December 2006

Changes in 2007 Pest Control Handbook – Peanut Weed Control Added Firestorm (generic paraquat) where appropriate Included Aim in burndown sections Added generic metolachlors but still included the following warning: The generic formulations of metolachlor (Parallel, Stalwart, Me-Too-Lachlor) have not provided the same length of residual control of certain weeds as similar rates of Dual Magnum formulations in some UGA field trials. Added a specific control rec for tropical spiderwort Table for ALS/GR-resistant pigweed control Added Propel (generic Outlook) Zorial to Solicam

Firestorm Chemtura –Great Lakes Chemical Corp. + Crompton Corp. 3 lb/gallon of paraquat Similar formulation as Gramoxone Max 5.4 to 10.8 ozs/A = normal rates

preplant burndown up to 24 hours after planting Up to 2 ozs/A –$5.00/oz Tank-mix with glyphosate

IMPOSE Generic liquid Cadre From Makhteshim Agan of North America (MANA)

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

Will these herbicides control large pigweeds?

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

4 ozs/A pt/A + 1% v/v – 34 DAT Applied to 17” tall pigweed

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

Palmer Amaranth Control with Cobra and 2,4-DB 12.5 ozs/A 1.1 pts/A 1% v/v Applied to 17” tall pigweed

How do we manage ALS-resistant Palmer amaranth? Need to start using more PRE’S –Valor, Dual Magnum/generics, Outlook –Goal????? POST Herbicides –Timeliness –Cobra, Ultra Blazer, Paraquat –Over reliance on PPO’s Will need both PRE’s and POST’s Increased production costs

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

What if we do not control Palmer amaranth? Crop (State)DensityYield LossSource Corn (KS) plants/m11-91%Weed Sci : Soybean (AK) plants/m17-68%Weed Sci : Grain sorghum (OK) 1-18 plants/15 m4-63%Weed Tech :23-29 Peanut (NC) 1-5 plants/m28-66%Burke and Wilcut (in-press) Cotton (TX) 1-10 plants/9.1 m13-54%Weed Tech :

Does Cobra reduce yields??

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

Classic Use in GA Peanuts

0.5 ozs/A Applied 62 DAE 7 DAT AP-3 GA-02C

11 weed-free field trials in GA 31 data points 77% ≤ 8% 23% > 8%

Classic Effects on Peanut Yield (P = 0.66)(P = 0.37) 0.5 oz/A % v/v Weed-free

Gramoxone Still Works!!!! (for me) Untreated Gramoxone Inteon (12 oz/A) + Storm (1.5 pt/A) + 80/20 (0.25% v/v) PE DAT

Speed, Nozzle Tip, GPA Effects 7 MPH Tractor Speed LSD 0.10 = 3

Gramoxone Inteon (GI) and Basagran (B) Effects on Peanut Yield GA-02C Averaged over 4 timings (7, 14, 22, 28 DAC) Included 0.25% v/v Weed-free P = 0.63

Cadre or Gramoxone fb Cadre??? 4 field trials conducted in lb/A average yield increase when Gramoxone + Basagran was used prior to Cadre compared to Cadre alone It only takes a 64 lbs/A increase of peanuts to pay for this treatment

Peanut (GA-02C) Response to Roundup Weathermax – 112 DAP

Roundup 12 ozs/A Applied 71 DAP 8 DAT

Peanut Yield Loss Caused by Roundup WeatherMax GA-O2C Ponder Farm