Soybean Weed Control Eric P. Prostko Extension Weed Specialist Department of Soil & Crop Science The University of Georgia

Conventional Soybean Weed Control Many Options Preemergence grasses – Treflan, Prowl, Dual/Generics, Intrro, Micro-Tech, Outlook, Command – grasses – Treflan, Prowl, Dual/Generics, Intrro, Micro-Tech, Outlook, Command – broadleaf – Boundary, Canopy, Sencor, Pursuit, Scepter, Lorox, Python, Valor, Reflex, Valor XLT, Envive, Prefix Postemergence –grasses – Assure/Targa, Fusilade, Poast, Select/Arrow – broadleaf – Ultra Blazer, Basagran, Cobra, Storm, Classic Rotation restrictions

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

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

RR Soybean Weed Control Systems Things to Think About glyphosate prices are increasing –$33/gal (generic 4 lb/gal) –$70/gal RUPM current price of RR soybean seed –$44/50 lbs (retail) weed resistance issues

R1 - first flower R2 - full bloom R3 - pod initiation R4 – full pod R5 – beginning seed R6 - Full seed

R2 R3

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 or  control weeds before the V3 stage Source: Purdue University Extension Weed Science Group (5.4 million acres harvested in in 2008)

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

Soybean Yield As Influenced by Glyphosate Applied at R4 + R6 Stage Source: Miller et al., Weed Technology 22: THSD 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 (Benghal Dayflower)

TSW in Georgia 2004: 29 counties (light blue) 2005: 5 counties (black) 2006: 6 counties (dark blue) 2007: 2 counties (yellow) 2008: 2 counties (red)

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

Tropical Spiderwort Control with Roundup WeatherMax in Soybean Ratings at DAT Average of 2 tests Roundup 22 ozs/A

Tropical Spiderwort Control in RR Soybeans Tattnall County Untreated 3 pts/A 3 pts/A 33 DAT

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

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) SelectMax (8-12 ozs/A) Poast (12-16 ozs/A) Poast Plus (18-24 ozs/A) adjuvants

Nutsedge Management in RR Soybeans preemergence –Canopy, Envive, Reflex, Dual –yellow nutsedge split applications of glyphosate –better on purple than yellow glyphosate + Classic –controls yellow –suppresses purple glyphosate + Pursuit –better on purple than yellow –rotations/cost

Glyphosate/Manganese Tank-Mixes depends upon type of Mn – Mn-EDTA (yes) – Mn-EAA (no) – Mn-LS (no) – MnS0 4 (no) 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: ); and Heckman et al., 1999 (Journal of Production Agriculture 12: )

Glyphosate Resistance Around the World (15 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) sourgrass (2006) junglerice (2007) liverseedgrass (2008) ** 9/15 (60%) can be found in the US

Georgia counties confirmed to be infested with glyphosate-resistant Palmer amaranth – 1 county 2005 – 2 counties 2006 – 7 counties 2007 – 10 counties 2008 – screening in progress

GA Confirmed ALS-Resistant Palmer Sites ALS Soybean Herbicides Classic, Scepter, Pursuit Python, Harmony, Synchrony

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

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

GR-Palmer Amaranth Control in Soybeans with PRE’s (2008) - Macon Co. NTC Canopy 6 oz/A SB DAT

GR-Pigweed Control in Soybeans SB Macon County 48 DAP NTC Canopy 6 oz/A + Prowl H 2 O 2.1 pt/A (PRE)

Metribuzin Products on Soybeans Sencor Boundary –Dual Magnum + Sencor Canopy –Sencor + Classic Read label Know soil texture and OM Varieties rotations

Crop Rotations for Metribuzin Products CropSencorBoundaryCanopy Field corn4 months8 months10 months wheat4 months4.5 months4 months cotton18 months8 months10 months peanut18 months12 months18 months sorghum18 months12 months

Soybean varieties screened in 2008 that had adequate tolerance to Boundary 6.5EC (2 pt/A), Canopy 75DG (5 oz/A), and Sencor 75DG (6 oz/A). Ag South AGS 568 Asgrow H7242 Asgrow 4903 RR/STS Delta Pineland DP 5634 Delta Pineland DP 6568 Northrup King NKS 80P2 Northrup King NKS 76L9Northrup King NKS 78G6 Pioneer 95Y40Pioneer 95Y70 Pioneer 96M60Pioneer 97M50 Southern States RT5951Southern States RT4808 Vigoro V61N9Vigoro V74N9

GR-Palmer Amaranth Control in Soybeans with PRE’s (2008) - Macon Co. NTC Prefix 2 pt/A SB DAT

GR-Palmer Amaranth Control in Soybeans with PRE’s (2008) - Macon Co. NTC Envive 3 oz/A SB DAT

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

Harmony GT XP or Harmony SG Harmony GT XP (75%) –GT = grass-tank mix –XP = extruded pellet Harmony SG (50%) –SG = soluble granules –1/8 oz/A 1 st trifoliate until 60 days before harvest tank-mix with glyphosate ALS inhibitor up to 12” tall pigweed????? variable amounts of soybean injury

Harmony GT on Soybeans (Tift County – 2008)

Harmony not Harmony Extra!!!!!

STS® Soybeans STS –Sulfonylurea Tolerant Soybeans Non-GMO first introduced in 1993 Synchrony XP –21.5% Classic + 6.9% Harmony –Non-STS POST Use Rate = oz/A 0.32 oz/A Classic 25DG oz/A Harmony GT –STS POST Use Rate = 0.75 oz/A 0.64 oz/A Classic 25DG oz/A Harmony GT 2007 UGA Soybean Variety Tests – DP5115RR/S, DP5335RR/S

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

Burning Wheat Stubble Good or Bad idea? probably not good if you need a residual herbicide for pigweed control Why?? may reduce the performance of residual herbicides –60% adsorption by ash

Weed Control in Soybeans Sicklepod Conventional * Canopy or Sencor or Python fb Classic Roundup Ready

What’s in the pipeline? Liberty-Link KIH-485 GAT Soybeans Dicamba, 2,4-D resistance

For More Weed Science Info