Slide Presentations-> Managing Palmer Amaranth in Peanut

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2009 Peanut Weed Management

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Eric P. Prostko
Extension Weed Specialist
Dept of Crop and Soil Sciences
UGA

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

Palmer Amaranth in Georgia

Some facts that should scare you! 1 Palmer amaranth plant per meter (3.2 ft) of row can reduce peanut yield by 28%. 1 Palmer amaranth plant per meter (3.2 ft) of crop row can result in the production of ~162,000,000 seed/acre. Source: Burke et al., 2007. Weed Technology 21:367-371

R-Palmer amaranth seed longevity Source: Dr. Lynn Sosnoskie - UGA

Palmer Amaranth Control in Peanuts Deep tillage or extreme cover crops Start Clean!!!!! Use a residual!!! Do you have ALS or DNA resistance? Are you willing to use Valor? Dryland or Irrigated? Spray when plants are small (<3”) Rope-wick Applications last resort

No Deep Tillage Deep Turn No Herbicide Treatment

Late-season Glyphosate-Resistant Palmer Control in Dryland Conservation Tillage Cotton. Macon Co., GA 2008.* 50 b 74 a Included: Prowl + Reflex PRE Roundup + Dual Magnum POST Direx + MSMA PD %

Weed-free Seedbed???

Palmer Amaranth Control in Peanuts Macon County, GA – 2007 (38 DAT) NTC Valor SX 51WG @ 3 oz/A

Palmer Amaranth Control in Peanuts Macon County, GA – 2007 (38 DAT) NTC Dual Magnum 7.62EC @ 1 pt/A

GR-Pigweed Control in Peanuts – 2008 Macon County – 91 DAP NTC Prowl H2O @ 2.1 pt/A (PRE) Valor SX 51WG @ 3 oz/A (PRE) Cadre 2AS @ 4 oz/A (41 DAP)+ Peptoil @ 1% v/v (41 DAP)

If residual herbicides are not activated on a timely basis with a reliable water source, pigweed control will be very difficult, maybe even impossible!

May 2008 Rainfall Distribution in Tifton (CPES) Dryland crops planted before May 9 or after May 16 did not get enough rain to activate residual herbicides!!! First rainfall event > 0.5” in June occurred on June 15 (1.03”) 0.33” 0.02” 0.06”

May-June 2008 Rainfall Distribution in Midville Crops planted from May 21-June 21 did not receive enough rainfall to activate herbicides (0.26” total). June Rainfall = 0.62” which occurred as follows:12 (0.08”); 22 (0.36”); 26 (0.08”); 29 (0.10”)

May-June 2008 Rainfall Distribution in Moultrie

Dryland Systems Growers need to think about mechanical herbicide incorporation Will help but not a guarantee Success will depend upon…… operator Implement Soil conditions Dual Magnum PPI (1 pt/A) POST (1 pt/A)

Can you mechanically incorporate Valor? Only labeled for PRE applications May lose 25-50% of weed control when mechanically incorporated (PPI) Valent not liable for reduced performance if applied PPI

Palmer Amaranth Control with Valor No-Till vs. Strip (40 DAT) Source: Culpepper Macon County C22-08

What about the generic formulations of metolachlor? Me-Too-Lachlor, Parallel PCS, Stalwart Frequently, but not always, they do not last as long as Dual Magnum

Palmer Amaranth Control in Peanut with Dual Magnum and Stalwart PE-03-07 Both applied at 1 pt/A *Significantly different at 53 DAT and 94 DAT (P = 0.10) * *

Will these herbicides control large pigweeds?

GR-Pigweed Control in Peanuts – 2008 Macon County – 91 DAP NTC Prowl H2O @ 2.1 pt/A (PRE) Gramoxone Inteon @ 12 oz/A (21 DAP) + Storm @ 1 pt/A + LI-700 @ 0.25% v/v (21 DAP) Cadre @ 4 ozA (41 DAP) + Peptoil @ 1% v/v (41 DAP)

GR-Pigweed Control in Peanuts – 2008 Macon County – 91 DAP NTC Prowl H2O @ 2.1 pt/A (PRE) Ultra Blazer @ 1 pt/A (21 DAP) + LI-700 @ 0.25% v/v (21 DAP) Cobra 2EC @ 12.5 oz/A (41 DAP) + Peptoil @ 1% v/v (41 DAP)

Palmer Amaranth Control with Ultra Blazer and 2,4-DB - 2008 NTC Ultra Blazer @ 1.5 pt/A LI-700 @ 0.25% v/v Treatments applied to 2-10” tall pigweed , 6.23” average height Photo 16 DAT Ultra Blazer @ 1.5 pt/A 2,4-DB @ 18 oz/A LI-700 @ 0.25% v/v

Palmer Amaranth Control with Cobra and 2,4-DB - 2008 NTC Cobra @ 12.5 oz/A 2,4-DB @ 18 oz/A Peptoil @ 1% v/v Treatments applied to 2-10” tall pigweed , 6.23” average height Photo 16 DAT Cobra @ 12.5 oz/A Peptoil @ 1% v/v

2,4-DB fb Cobra or Ultra Blazer????? (has only been successful ¼ times) POST: June 5 (17” tall pigweed) POST2: June 9 Photos taken 24 days after POST application 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

Rope-wick Applicators Only thing labeled (sort of) is glyphosate Label says row middles At this time of year, yields not influenced Benefits Harvestability Fungicide spray deposition Seed bank REVENGE!!!!

Custer’s Last Stand

Possible Herbicide Programs (Assuming ALS Resistance) Irrigated Prowl/Sonalan + Valor (PRE) Cobra or Ultra Blazer + Dual Magnum (POST) 2-3” tall pigweed Dryland Prowl/Sonalan (PPI) Paraquat + Storm + Dual Magnum (CRACK) Cobra or Ultra Blazer + Dual Magnum (POST) 2-3” tall pigweed Total Maximum Amount of Dual Magnum that can used per year is 45 oz/A 90 day PHI

We are overusing the PPO inhibiting herbicides!!!!!!!! Resistance has already been reported in other areas!!! Common waterhemp 2001 (Kansas) 2002 (Illinois) 2003 (Missouri) Common ragweed 2005 (Delaware) Wild poinsettia 2004 (Brazil)

For More Weed Science Info www.gaweed.com www.gaweed.com

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