This document summarizes weed control strategies for soybeans in 2011. It recommends using pre-emergence herbicides which provide early-season control and reduce in-season weed pressure, potentially increasing yields by 1 bushel per acre. It discusses several herbicide options for pre-emergence, fall, and burndown applications. It also stresses starting with a clean field by burning down weeds before planting, scouting regularly to spray small weeds, and using tank mixes to control difficult weeds. Finally, it provides contact information for the speaker and links to resources on herbicide resistance testing in Oklahoma.

1. Recipe for Success:Weed Control in 2011OK Soy Expo Joe Armstrong Extension Weeds Specialist

3. Authority XL FMC Pre-mix of Authority & Classic Use rates: 3.0 – 9.6 oz/acre Fall and PRE applications 4.0 oz = 3.33 oz Authority DF 1.25 oz Classic *36 month rotation restriction for canola

4. Warrant Monsanto Sold as MON 63410 in 2010 Use rate: 3 pints/acre Apply Early POST, V2 – V3 growth stage Tank-mix with POST product(s)

5. Verdict BASF Pre-mix of Sharpen & Outlook Use rate: 5 – 10 floz/acre Fall, burndown, and PRE applications 5.0 floz = 1 floz Sharpen 4.17 floz Outlook

6. Fierce Valent Pre-mix of Valor & pyroxysulfone Use rate: 3 – 4.5 oz/acre Fall, burndown, and PRE applications 3.0 oz = 2.0 oz Valor 1.5 ozpyroxysulfone *Not currently labeled for use in OK

7. What is the #1 goal of weed control? (Hint: it’s not always killing weeds)

10. Less in-season weed pressure

13. PRE herbicides inno-till soybean (NW OK) glyphosate + 2,4-D alone 7 weeks after treatment All treatments included glyphosate + 2,4-D ester (32 fl oz + 1 pt)

14. PRE herbicides inno-till soybean (NW OK) glyphosate + 2,4-D alone 7 weeks after treatment All treatments included glyphosate + 2,4-D ester (32 fl oz + 1 pt)

16. Early POST with residual

17. Herbicide resistance testing update

18. Glyphosate-resistant marestail in Oklahoma Resistant Susceptible Untreated 1x glyphosate (0.75 lbae) 2x glyphosate (1.5 lbae) 4x glyphosate (3.0 lbae) Grant County, 2010

19. PSS-2779 “Diagnostic Service to Test for Herbicide-resistant Weeds in Oklahoma”www.weedscience.okstate.edu

22. Burndown before planting—start clean

23. Tank-mix to control difficult weeds

25. Contact information Joe Armstrong OSU Dept. of Plant and Soil Sciences joe.armstrong@okstate.edu Twitter: @OSUWeedSci www.weedscience.okstate.edu