Soybean Weed

Control

Eric P. ProstkoExtension Weed Specialist

Department of Soil & Crop ScienceThe University of Georgia

Conventional Soybean Weed ControlMany Options

• Preemergence– grasses grasses –– Treflan, Prowl, Dual/Generics, Intrro, MicroTreflan, Prowl, Dual/Generics, Intrro, Micro--Tech, Tech,

Outlook, CommandOutlook, Command–– broadleaf broadleaf –– Boundary, Canopy, Sencor, Pursuit, Scepter, Boundary, Canopy, Sencor, Pursuit, Scepter,

Lorox, Python, Valor, Reflex, Valor XLT , Envive, PrefixLorox, Python, Valor, Reflex, Valor XLT , Envive, Prefix

• Postemergence–– grasses grasses –– Assure/Targa, Fusilade, Poast, Select/ArrowAssure/Targa, Fusilade, Poast, Select/Arrow–– broadleaf broadleaf –– Ultra Blazer, Basagran, Cobra, Storm, ClassicUltra 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

54

6875

81 85 87 89 91 92

0

20

40

60

80

100

2000 2001 2002 2003 2004 2005 2006 2007 2008

Year

% o

f Acr

es

.

Source: NASS

RR Soybean Weed Control SystemsThings 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 bloomR3 - pod initiation R4 – full podR5 – beginning seed R6 - Full seed

R2

R3

To Prevent Yield Loss in RR Soybeans

1 control weeds by 4-5 weeks after planting

or2 control weeds before they

reach 6-9” in heightor

3 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)

05

1015202530354045

2000 2001

Year

Bu/

A

V3 R2 R4 V3+R2 V3+R4 V3+R6 NTC

J.K. Norsworthy. 2004. Weed Technology 18:454-457 LSD 0.05 = NS

Soybean Yield As Influenced by Glyphosate Applied at R4 + R6 Stage

51 5148 50 52

49

0

15

30

45

60

0 0.41 0.82 1.23 1.64 2.45

Glyphosate Rate (lb ae/A)

Bu/

A

>

Source: Miller et al., 2008. Weed Technology 22:359-362 THSD 0.05 = NS

Glyphosate + Fungicide Tank-MixesSoybean 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/DimilinTank 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 -2004

62

8377

71

0

20

40

60

80

100

None Pursuit (4 ozs) Classic (0.5 ozs) FirstRate (0.20ozs)

Tank-Mix

Con

trol -

%

.

Ratings at 20-24 DATAverage of 2 testsRoundup WeatherMax @ 22 ozs/A

Tropical Spiderwort Control in RR Soybeans

Tattnall County - 2005

Untreated Sequence @ 3 pts/A Extreme @ 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. 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)• 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)– MnS04 (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 16:792-799); and Heckman et al., 1999 (Journal of Production Agriculture 12:445-448)

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.

2004 – 1 county

2005 – 2 counties

2006 – 7 counties

2007 – 10 counties

2008 – screening in progress

GA Confirmed ALS-Resistant Palmer Sites

ALS Soybean HerbicidesClassic, Scepter, PursuitPython, Harmony, Synchrony

Soybean Yield Losses Caused by Palmer Amaranth Plants When They Emerge with Crop

13

33

68

0

20

40

60

80

100

0.32 1.1 9.8

Density (plants/meter)

%

Klingman and Oliver. 1994. Weed Sci. 42:523-527

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 75WG @ 6 oz/ASB-05-0848 DAT

GR-Pigweed Control in Soybeans - 2008

SB-06-08Macon County48 DAP

NTC Canopy 75DG @ 6 oz/A + Prowl H2O 3.8ASC @ 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 forMetribuzin Products

18 months12 months18 monthspeanut

12 months12 months18 monthssorghum

10 months8 months18 monthscotton

4 months4.5 months4 monthswheat

10 months8 months4 monthsField corn

CanopyBoundarySencorCrop

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 76L9 Northrup King NKS 78G6• Pioneer 95Y40 Pioneer 95Y70• Pioneer 96M60 Pioneer 97M50• Southern States RT5951 Southern States RT4808• Vigoro V61N9 Vigoro V74N9

GR-Palmer Amaranth Control in Soybeans with PRE’s (2008) - Macon Co.

NTC Prefix 5.29EC @ 2 pt/ASB-05-0848 DAT

GR-Palmer Amaranth Control in Soybeans with PRE’s (2008) - Macon Co.

NTC Envive 41.3WG @ 3 oz/ASB-05-0848 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

• 1st 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 = 0.375 oz/A

• 0.32 oz/A Classic 25DG + 0.035 oz/A Harmony GT– STS POST Use Rate = 0.75 oz/A

• 0.64 oz/A Classic 25DG + 0.07 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 StubbleGood 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 SoybeansSicklepod

• 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

www.gaweed.com