1. 2008 Soybean Weed Control Update
Dr. Eric P. Prostko
Extension Weed Specialist
The University of Georgia

2. 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

3. 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

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

5. 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

6. 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

7. 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)

8. 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 Weed Technology 18:
LSD 0.05 = NS

9. 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

10. 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

11. Tropical Spiderwort

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

13. 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

14. Tropical Spiderwort Control in RR Soybeans Tattnall County - 2005
Untreated
3 pts/A
3 pts/A
33 DAT

15. 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

16. 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

17. 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

18. 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

19. 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: ); and Heckman et al., 1999
(Journal of Production Agriculture 12: )

20. 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

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

22. GA Confirmed ALS-Resistant Palmer Sites

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

24. 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!!!!!!

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

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

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

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

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

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

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

32. 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

33. Harmony GT XP in Soybeans (2007)

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