2008 Soybean Weed 2008 Soybean Weed Control UpdateControl Update

Dr. Eric P. ProstkoDr. Eric P. ProstkoExtension Weed SpecialistExtension Weed SpecialistThe University of GeorgiaThe University of Georgia

Burndown Options for Reduced Tillage Burndown Options for Reduced Tillage Soybean Production SystemsSoybean Production Systems

PrimaryPrimary– Glyphosate– Gramoxone

Inteon/Firestorm/Parazone– Ignite

Tank-mixesTank-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 ControlConventional Soybean Weed ControlBack toBack to The Future?The Future?

PreemergencePreemergence– grasses – Treflan, Prowl, Dual/Generics, Intrro, Micro-grasses – Treflan, Prowl, Dual/Generics, Intrro, Micro-

Tech, Outlook, CommandTech, Outlook, Command– broadleaf – Boundary, Canopy, Sencor, Pursuit, broadleaf – Boundary, Canopy, Sencor, Pursuit,

Scepter, Lorox, Python, Valor, Reflex, Valor XLT Scepter, Lorox, Python, Valor, Reflex, Valor XLT – many pre-mixesmany pre-mixes

PostemergencePostemergence– grasses – Assure/Targa, Fusilade, Poast, Select/Arrowgrasses – Assure/Targa, Fusilade, Poast, Select/Arrow– broadleaf – Ultra Blazer, Basagran, Cobra, Storm, broadleaf – Ultra Blazer, Basagran, Cobra, Storm,

ClassicClassic

Rotation restrictionsRotation restrictions

U.S. Soybean Acres Planted to U.S. Soybean Acres Planted to Herbicide Resistant VarietiesHerbicide Resistant Varieties

54

6875

81 85 87 89 91

0

20

40

60

80

100

2000 2001 2002 2003 2004 2005 2006 2007

Year

% o

f Ac

res

Source: NASSSource: NASS - Prospective Plantings

RR Soybean Weed Control SystemsRR Soybean Weed Control SystemsThings to Think AboutThings to Think About

glyphosate prices are glyphosate prices are increasingincreasing– $22/gal (generic 4 lb/gal)

current price of RR current price of RR soybean seedsoybean seed– $35/50 lbs (retail)

weed resistance issuesweed resistance issues

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

Soybean Growth Stages

To Prevent Yield Loss in RR SoybeansTo Prevent Yield Loss in RR Soybeans

control weeds by 4-5 control weeds by 4-5 weeks after plantingweeks after planting

oror control weeds before control weeds before

they reach 6-9” in they reach 6-9” in heightheight

oror control weeds before control weeds before

the V3 stagethe 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 Tolerance of GR-Soybean to Late-Season Glyphosate Applications (1.5 lb ai/A)Glyphosate Applications (1.5 lb ai/A)

0

5

10

15

20

25

30

35

40

45

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

Glyphosate + Fungicide Tank-MixesGlyphosate + Fungicide Tank-MixesSoybean RustSoybean Rust

What do labels say?What do labels say? timing concernstiming concerns

– Glyphosate = V3– Fungicide = R1 or later

limited informationlimited information preliminary results preliminary results

from UGA research from UGA research suggest no major suggest no major problems problems

more data is neededmore data is needed

Glyphosate/Boron/DimilinGlyphosate/Boron/DimilinTank MixesTank Mixes

full-bloom to early pod-full-bloom to early pod-fillfill

R2-R3 stageR2-R3 stage Is this the best time for Is this the best time for

Roundup? (V3)Roundup? (V3) Crop injury?Crop injury? No more than 0.25 to No more than 0.25 to

0.5 lb/A of Boron0.5 lb/A of Boron

Tropical SpiderwortTropical Spiderwort

Tropical Spiderwort in GeorgiaTropical 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 Tropical Spiderwort Management in RR SoybeansRR Soybeans

timing is criticaltiming is critical EPOSTEPOST

– 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 Tropical Spiderwort Control in RR Soybeans Tattnall County - 2005Tattnall County - 2005

Untreated Sequence @ 3 pts/A Extreme @ 3 pts/A

33 DAT

Conventional Soybean SystemsConventional Soybean SystemsTropical Spiderwort ControlTropical Spiderwort Control

preemergencepreemergence– Dual Magnum (s-metolachlor), Generics– Boundary (Sencor + Dual Magnum)– Pursuit– postemergence– Basagran, Classic, Pursuit, FirstRate– must be timely!

Post-directed/hooded sprayerPost-directed/hooded sprayer– Gramoxone Max (8’’/3”) or Aim

Controlling RR Cotton in RR SoybeansControlling RR Cotton in RR Soybeans

PreemergencePreemergence– Canopy 75DG (8 oz/A)– Sencor 4L (8-12 oz/A) – Sencor 75DF (5.3-8 oz/A)

POST glyphosate tank-mixesPOST 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%PRE only = 54-87% POST only = 62-77%POST only = 62-77% PRE + POST = > 95% PRE + POST = > 95%

Source: York et al., Weed Technology. 2004. 532-539.

Controlling RR Corn in RR SoybeansControlling RR Corn in RR Soybeans

tank-mix glyphosate with tank-mix glyphosate with POST grass herbicidePOST grass herbicide

rate depends on height of rate depends on height of corncorn

Assure II (5-8 ozs/A)Assure II (5-8 ozs/A) Fusilade (4-8 ozs/A)Fusilade (4-8 ozs/A) Select (4-8 ozs/A)Select (4-8 ozs/A) Select-Max (8-12 ozs/A)Select-Max (8-12 ozs/A) Poast (12-16 ozs/A)Poast (12-16 ozs/A) Poast Plus (18-24 ozs/A)Poast Plus (18-24 ozs/A) adjuvantsadjuvants

Nutsedge Management in RR SoybeansNutsedge Management in RR Soybeans split applications of split applications of

glyphosateglyphosate– better on purple than yellow

tank-mix with Classic tank-mix with Classic – controls yellow – suppresses purple

tank-mix with Pursuittank-mix with Pursuit– better on purple than yellow– rotations/cost

Glyphosate/Manganese Tank-MixesGlyphosate/Manganese Tank-Mixes

depends upon type of depends upon type of MnMn– Mn-EDTA (yes)– Mn-EAA (no)– Mn-LS (no)

– MnS04 (no)

use AMSuse AMS Mn not a problem with Mn not a problem with

Blazer, Classic, Pursuit, Blazer, Classic, Pursuit, or Basagran.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 Glyphosate Resistance Around the World (13 species)(13 species)

rigid ryegrass (1996)rigid ryegrass (1996) goosegrass (1997)goosegrass (1997) horseweed (2000)horseweed (2000) Italian ryegrass (2001)Italian ryegrass (2001) hairy fleabane (2003)hairy fleabane (2003) buckhorn plantain (2003)buckhorn plantain (2003) common ragweed (2004)common ragweed (2004) giant ragweed (2004)giant ragweed (2004) Palmer amaranth (2005)Palmer amaranth (2005) common waterhemp (2005)common waterhemp (2005) johnsongrass (2005)johnsongrass (2005) wild poinsettia (2005)wild poinsettia (2005) johnsongrass (2005)johnsongrass (2005)

** Can be found in the US

GA Confirmed Glyphosate-Resistant Palmer SitesGA Confirmed Glyphosate-Resistant Palmer Sites

2005

2006

Current Testing2007

GA Confirmed ALS-Resistant Palmer SitesGA Confirmed ALS-Resistant Palmer Sites

Soybean Yield Losses Caused by Soybean Yield Losses Caused by Palmer Amaranth Plants When They Palmer Amaranth Plants When They Emerge with CropEmerge 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 SoybeansPigweed Control in Soybeans

use a residual herbicideuse a residual herbicide

– Valor, Valor XLT, Prefix, Dual Magnum/Generics, Sencor, Boundary, Prowl, Treflan

ALS or Glyphosate ALS or Glyphosate Resistance!!!!Resistance!!!!

Spray POST herbicides Spray POST herbicides early!!!!!!early!!!!!!

Untreated Roundup WM @ 22 oz/A + Cobra 12.5 oz/A

(POST)

GR-Pigweed Control without a residual herbicide!GR-Pigweed Control without a residual herbicide!

GR-Palmer Amaranth Control in Soybean (2007) GR-Palmer Amaranth Control in Soybean (2007) (83 DAT)(83 DAT)

Untreated Boundary 6.5EC @ 1.8 pt/ASB-01-07

GR-Palmer Amaranth Control in Soybean (2007)GR-Palmer Amaranth Control in Soybean (2007) (83 DAT) (83 DAT)

Untreated Dual Magnum 7.62EC @ 1.33 pt/ASB-01-07

GR-Palmer Amaranth Control in Soybean (2007)GR-Palmer Amaranth Control in Soybean (2007) (83 DAT) (83 DAT)

Untreated Prefix 5.2EC @ 2.03 pt/ASB-01-07

GR-Palmer Amaranth Control in Soybean (2007)GR-Palmer Amaranth Control in Soybean (2007) (77 DAT) (77 DAT)

Untreated Valor SX 51WG @ 3 oz/ASB-02-07

GR-Palmer Amaranth Control in Soybean (2007)GR-Palmer Amaranth Control in Soybean (2007) (77 DAT) (77 DAT)

Untreated Valor XLT 40WG @ 5 oz/ASB-02-07

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

Harmony GT XP or Harmony SGHarmony GT XP or Harmony SG

Harmony GT XP (75%)Harmony GT XP (75%)– GT = grass-tank mix– XP = extruded pellet– 1/12 oz/A ($1.17)

Harmony SG (50%)Harmony SG (50%)– SG = soluble granules– 1/8 oz/A

11stst trifoliate until 60 days before harvest trifoliate until 60 days before harvest tank-mix with glyphosatetank-mix with glyphosate ALS inhibitorALS inhibitor up to 12” tall pigweed?????up to 12” tall pigweed????? Soybean injurySoybean injury

Harmony GT XP in Soybeans (2007)Harmony GT XP in Soybeans (2007)

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

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