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2008 Soybean Weed Control Update Dr. Eric P. Prostko Extension Weed Specialist

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)

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2008 Soybean Weed Control Update Dr. Eric P. Prostko Extension Weed Specialist

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  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 ControlBack toThe 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 SystemsThings 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 or • 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 (1.5 lb ai/A) J.K. Norsworthy. 2004. Weed Technology 18:454-457 LSD 0.05 = NS

  9. 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

  10. 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

  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 Sequence @ 3 pts/A Extreme @ 3 pts/A 33 DAT

  15. Conventional Soybean SystemsTropical 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. 2004. 532-539.

  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 • better on purple than yellow • 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 16:792-799); and Heckman et al., 1999 (Journal of Production Agriculture 12:445-448)

  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) • johnsongrass (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. 1994. Weed Sci. 42:523-527

  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 WM @ 22 oz/A + Cobra 12.5 oz/A (POST)

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

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

  28. GR-Palmer Amaranth Control in Soybean (2007) (83 DAT) Untreated Prefix 5.2EC @ 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 • Harmony GT XP (75%) • 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!!!!

  35. www.gaweed.com

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