This document summarizes weed control strategies for soybeans in 2011. It discusses several pre-emergence herbicide options including Authority XL, Warrant, Verdict, and Fierce. It emphasizes that the number one goal of weed control is yield, not just killing weeds. Pre-emergence herbicides improve early-season control and reduce in-season weed pressure, potentially increasing yields by as little as 1 bushel per acre. Weeds begin reducing yields very early, as little as 2-3 weeks after emergence. The document recommends using pre-emergence herbicides, burndown before planting, tank-mixing for difficult weeds, and spraying when weeds are small. It also provides an

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

2. 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

3. 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)

4. 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

5. 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

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

7. Yield!

9. Less in-season weed pressure

12. 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)

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)

15. Early POST with residual

16. Herbicide resistance testing update

17. 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

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

20. Burndown before planting—start clean

21. Tank-mix to control difficult weeds

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