2008 Soybean Weed Control Update Dr. Eric P. Prostko Extension Weed Specialist The University of Georgia

Burndown Options for Reduced Tillage Soybean Production Systems Primary Glyphosate Gramoxone Inteon/Firestorm/Parazone Ignite Tank-mixes 2,4-D (7-15 DBP) Aim (0 DBP) ET (0 DBP) Valor (0 DBP) Harmony Extra (14 DBP) Express (14 DBP) Clarity/Vision (14 DBP + 1” rainfall) Canopy EX (Classic + Express) 7-14 DBP DBP = days before planting

Conventional Soybean Weed Control Back to The Future? Preemergence grasses – Treflan, Prowl, Dual/Generics, Intrro, Micro-Tech, Outlook, Command broadleaf – Boundary, Canopy, Sencor, Pursuit, Scepter, Lorox, Python, Valor, Reflex, Valor XLT many pre-mixes Postemergence grasses – Assure/Targa, Fusilade, Poast, Select/Arrow broadleaf – Ultra Blazer, Basagran, Cobra, Storm, Classic Rotation restrictions

U.S. Soybean Acres Planted to Herbicide Resistant Varieties Source: NASS - Prospective Plantings Source: NASS

RR Soybean Weed Control Systems Things to Think About glyphosate prices are increasing $22/gal (generic 4 lb/gal) current price of RR soybean seed $35/50 lbs (retail) weed resistance issues

Soybean Growth Stages V3 stage occurs when 3 trifoliolates are fully developed above the unifoliate leaves R1 stage occurs when one open flower is at any node on the main stem

To Prevent Yield Loss in RR Soybeans control weeds by 4-5 weeks after planting or control weeds before they reach 6-9” in height control weeds before the V3 stage Source: Purdue University Extension Weed Science Group (4.32 million acres of RR soybeans planted in 2007)

Tolerance of GR-Soybean to Late-Season Glyphosate Applications (1 Tolerance of GR-Soybean to Late-Season Glyphosate Applications (1.5 lb ai/A) J.K. Norsworthy. 2004. Weed Technology 18:454-457 LSD 0.05 = NS

Glyphosate + Fungicide Tank-Mixes Soybean Rust What do labels say? timing concerns Glyphosate = V3 Fungicide = R1 or later limited information preliminary results from UGA research suggest no major problems more data is needed

Glyphosate/Boron/Dimilin Tank Mixes full-bloom to early pod-fill R2-R3 stage Is this the best time for Roundup? (V3) Crop injury? No more than 0.25 to 0.5 lb/A of Boron

Tropical Spiderwort

Tropical Spiderwort in Georgia 2004: 29 counties (light blue) 2005: 5 counties (black) 2006: 6 counties (dark blue) 2007: 2 counties (yellow)

Tropical Spiderwort Management in RR Soybeans timing is critical EPOST Sequence (3 pts/A) Glyphosate + Dual Magnum Extreme (3 pts/A) Glyphosate + Pursuit glyphosate + Pursuit or Classic or FirstRate

Tropical Spiderwort Control in RR Soybeans Tattnall County - 2005 Untreated Sequence @ 3 pts/A Extreme @ 3 pts/A 33 DAT

Conventional Soybean Systems Tropical Spiderwort Control preemergence Dual Magnum (s-metolachlor), Generics Boundary (Sencor + Dual Magnum) Pursuit postemergence Basagran, Classic, Pursuit, FirstRate must be timely! Post-directed/hooded sprayer Gramoxone Max (8’’/3”) or Aim

Controlling RR Cotton in RR Soybeans Preemergence Canopy 75DG (8 oz/A) Sencor 4L (8-12 oz/A) Sencor 75DF (5.3-8 oz/A) POST glyphosate tank-mixes 6” cotton, 3 leaves Resource (4 ozs/A) - 77% 2,4-DB (2 ozs/A) - 76% Reflex (12 ozs/A) - 72% Classic (0.33 ozs/A) - 62% PRE only = 54-87% POST only = 62-77% PRE + POST = > 95% Source: York et al., Weed Technology. 2004. 532-539.

Controlling RR Corn in RR Soybeans tank-mix glyphosate with POST grass herbicide rate depends on height of corn Assure II (5-8 ozs/A) Fusilade (4-8 ozs/A) Select (4-8 ozs/A) Select-Max (8-12 ozs/A) Poast (12-16 ozs/A) Poast Plus (18-24 ozs/A) adjuvants

Nutsedge Management in RR Soybeans split applications of glyphosate better on purple than yellow tank-mix with Classic controls yellow suppresses purple tank-mix with Pursuit rotations/cost

Glyphosate/Manganese Tank-Mixes depends upon type of Mn Mn-EDTA (yes) Mn-EAA (no) Mn-LS (no) MnS04 (no) use AMS Mn not a problem with Blazer, Classic, Pursuit, or Basagran. Sources: Bernards et al., 2005 (Weed Technology 19:27-34; Bailey et al., 2002 (Weed Technology 16:792-799); and Heckman et al., 1999 (Journal of Production Agriculture 12:445-448)

Glyphosate Resistance Around the World (13 species) rigid ryegrass (1996) goosegrass (1997) horseweed (2000) Italian ryegrass (2001) hairy fleabane (2003) buckhorn plantain (2003) common ragweed (2004) giant ragweed (2004) Palmer amaranth (2005) common waterhemp (2005) johnsongrass (2005) wild poinsettia (2005) ** Can be found in the US

GA Confirmed Glyphosate-Resistant Palmer Sites 2005 2006 Current Testing 2007

GA Confirmed ALS-Resistant Palmer Sites

Soybean Yield Losses Caused by Palmer Amaranth Plants When They Emerge with Crop Klingman and Oliver. 1994. Weed Sci. 42:523-527

Pigweed Control in Soybeans use a residual herbicide Valor, Valor XLT, Prefix, Dual Magnum/Generics, Sencor, Boundary, Prowl, Treflan ALS or Glyphosate Resistance!!!! Spray POST herbicides early!!!!!!

GR-Pigweed Control without a residual herbicide! Untreated Roundup WM @ 22 oz/A + Cobra 12.5 oz/A (POST)

GR-Palmer Amaranth Control in Soybean (2007) (83 DAT) Untreated Boundary 6.5EC @ 1.8 pt/A SB-01-07

GR-Palmer Amaranth Control in Soybean (2007) (83 DAT) Untreated Dual Magnum 7.62EC @ 1.33 pt/A SB-01-07

GR-Palmer Amaranth Control in Soybean (2007) (83 DAT) Untreated Prefix 5.2EC @ 2.03 pt/A SB-01-07

GR-Palmer Amaranth Control in Soybean (2007) (77 DAT) Untreated Valor SX 51WG @ 3 oz/A SB-02-07

GR-Palmer Amaranth Control in Soybean (2007) (77 DAT) Untreated Valor XLT 40WG @ 5 oz/A SB-02-07

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

Harmony GT XP or Harmony SG GT = grass-tank mix XP = extruded pellet 1/12 oz/A ($1.17) Harmony SG (50%) SG = soluble granules 1/8 oz/A 1st trifoliate until 60 days before harvest tank-mix with glyphosate ALS inhibitor up to 12” tall pigweed????? Soybean injury

Harmony GT XP in Soybeans (2007)

Be careful when mixing!! Staple, Envoke, Cadre not a good idea!!!!

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