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 100 Percent (%) viable 90 80 70 60 0.5" 1" 50 4" 16" 40 0 mon. 3 mon. 6 mon. 9 mon. Length of burial 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.* W heat cover Rye cover 80 74 a 60 50 b 40 % 20 0 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) Dual Magnum 7.62EC NTC @ 1 pt/A
GR-Pigweed Control in Peanuts – 2008 Macon County – 91 DAP Prowl H 2 O @ 2.1 pt/A (PRE) NTC 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) 1.6 1.4 1.2 1 0.8 0.6 0.33” 0.4 0.2 0.06” 0.02” 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 Day 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”)
May-June 2008 Rainfall Distribution in Midville 1.6 1.6 1.4 1.4 1.2 1.2 1 1 0.8 0.8 0.6 0.6 0.4 0.4 0.2 0.2 0 0 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 13 14 15 16 17 18 19 20 2 1 2 2 2 3 24 25 26 27 28 29 30 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 May June 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 1 1 0.8 0.8 0.6 0.6 0.4 0.4 0.2 0.2 0 0 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 13 14 15 16 17 18 19 20 2 1 2 2 2 3 24 25 26 27 28 29 30 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 May June
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) Strip N o-Till 100 89 80 86 . 81 ontrol - % 60 60 53 53 50 40 C 20 13 0 1 2 3 4 Valor R ate/A 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 Dual M agnum Stalwart 100 Control - % . * 80 * 60 40 20 0 11 18 23 38 53 94 Tim e (DAT) 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 Prowl H 2 O @ 2.1 pt/A (PRE) NTC 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 Prowl H 2 O @ 2.1 pt/A (PRE) NTC 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 Ultra Blazer @ 1.5 pt/A Ultra Blazer @ 1.5 pt/A NTC LI-700 @ 0.25% v/v 2,4-DB @ 18 oz/A LI-700 @ 0.25% v/v Treatments applied to 2-10” tall pigweed , 6.23” average height Photo 16 DAT
Palmer Amaranth Control with Cobra and 2,4-DB - 2008 Cobra @ 12.5 oz/A Cobra @ 12.5 oz/A NTC 2,4-DB @ 18 oz/A Peptoil @ 1% v/v Peptoil @ 1% v/v Treatments applied to 2-10” tall pigweed , 6.23” average height Photo 16 DAT
2,4-DB fb Cobra or Ultra Blazer????? (has only been successful ¼ times) 2,4-DB 1.75SL @ 1.1 pt/A + Untreated Cobra 2EC @ 12.5 oz/A Agrioil @ 1% v/v (POST) Agrioil @ 1% v/v fb POST 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
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
Recommend
More recommend
