1. Herbicide-Resistant Weeds: A Dilemma in Dixie Culpepper, York, Steckel, Prostko

2. What is Herbicide Resistance? (official WSSA definition) Inherited ability of a biotype of a weed to survive and reproduce following exposure to a dose of herbicide normally lethal to the wild type.

3. WeatherMax 22 oz, 2 d after application to 16 inch Palmer

4. WeatherMax 33 oz/A on 3” Palmer

5. Reported cases of herbicide-resistant weeds in US

8. Why is Resistance Such a Big Deal Now?

9. 1. ALS resistant pigweeds 2.Glyphosate-resistant horseweed 3.Glyphosate-resistant ragweed 4.Glyphosate-resistant lambsquarters* 5.Glyphosate-resistant Italian ryegrass* 1. Glyphosate-resistant Palmer amaranth (pigweed) Significant Potentially Devastating *suspected not confirmed

10. 97 94 00 ALS*-resistant Amaranthus species *Imidazolinones, sulfonylureas, 19 states triazolopyrimidines, pyrimidinylthiobenzoates 94 02 94 95 00 92 98 99 02 93 98 96 93 91 99

11. Commonly Used ALS Herbicides Accent Ally/Cimarron Beacon Beyond Cadre Classic Envoke Exceed Express Finesse FirstRate Glean Harmony Extra Maverick Pro Osprey Peak Permit Pursuit Python Scepter Staple Strongarm

12. Prostko 2006 2005 ALS-Resistant Pigweed Survey 61 locations, 21 counties 2892 plants treated 2442 plants survived (84%)

13. 100 66 97 99 98 99 100 98 83 9775 97 59 Percent of cotton acreage planted to RR varieties. 2006 1 1 USDA, AMS. 2006. Publ. mp-cn833.

14. 96 97 98 99 00 01 02 03 04 05 06 98 99 00 01 02 03 04 05 06 97 98 99 00 01 02 03 04 05 06 Adoption of Roundup Ready Technology in the US (million acres) Soybean Corn Cotton

17. Very Small Seeded Approximately 1 mm

18. Shields, E.J., J.T. Dauer, M.J. VanGessel, and G. Neuman. 2006. Horseweed (Conyza canadensis) seed collected in the planetary boundary layer. Weed Sci. 54:1063-1067. Altitude (ft) 230 460 Seeds found (#/1000 m 3 )* 3.3 1.7 * Approximately 33 by 33 by 33 ft

19. Photo credit: Larry Steckel Must Start Clean!

20. Photo credit: Larry Steckel

21. GR Horseweed Control 020406080100 Roundup WM 22oz Clarity 8 oz + Roundup WM 22oz Ignite 23 oz LSD = 12 % Horseweed Control Milan May 28, 2006 2,4-D 16 oz + Roundup WM 22oz Burndown applied 4/3/06 Clarity 8 oz + Roundup WM 22oz fb/Gramoxone Inteon 40 oz + Caparol 24oz Clarity 8 oz + Roundup WM 22oz fb/ Roundup WM 22oz + Cotoran 24oz

22. HORSEWEED Preferred Burndown Options 1.Roundup + ½ pt Clarity, mid March 2.Roundup + 2 pt 2,4-D, mid March With either of above, consider a residual herbicide with the burndown, such as Valor. If no residual, Gramoxone + Cotoran or Direx at planting or Ignite + Cotoran or Direx at planting.

23. 2004 Common Horseweed Burndown Program Photo credit: Larry Steckel

24. Rapid Growth Becoming Extremely Large

25. Average Number of Seed Produced per Plant 400,000 40,000 9,000 0 50,000 100,000 150,000 200,000 250,000 300,000 350,000 400,000 450,000 Palmer Amaranth goosegrassannual bluegrass common cocklebur Top 4 Herbicide Resistant Weeds in US peanut - 175; cotton - 250; corn - 800

26. Attapulgus GA, September 2004 Multiple Generations – Short Seed Dormancy

27. Untreated Georgia, 2006 Glyphosate 4X rate, applied three times Palmer Amaranth Infesting Cotton

28. North Carolina, 2006 Untreated Glyphosate 4X rate, applied three times Palmer Amaranth Infesting Cotton

29. Cotton Yield vs. Palmer Competition 7%

30. Glyphosate-resistant Palmer Amaranth Found 04 05 * * * * Palmer populations being studied for resistance.

31. Resistance trait will move through pollen

32. Managing Glyphosate Resistance

33. Georgia and North Carolina Recommendations* At Planting Topical (1-to 4 lf cotton)Layby Directed Yellow + Reflex Glyphosate + Dual Magnum (no emerged Palmer) MSMA + Diuron MSMA + Layby Pro MSMA + Suprend MSMA + Valor Glyphosate + Staple (Palmer 1-2”) *Cultivation, Hooded Sprays, and/or Hand Weeding Will be Required

34. Prowl H20 1.75 pt + Reflex 1 pt PRE WeatherMax 22 oz + Dual Mag 18 DAP before Pigweed emergence WeatherMax 22 oz + Direx 1.5 pt PDIR

35. Prowl H20 1.75 pt + Reflex 1 pt PRE WeatherMax 22 oz + Dual Mag 24 DAP with ½” Palmer WeatherMax 22 oz + Direx 1.5 pt PDIR

36. Prowl + Reflex PRE Roundup + Staple 3 inch Direx + MSMA PD

37. Prowl H20 1.75 pt + Reflex 1 pt PRE WeatherMax 22 oz + Staple at 3 inch WeatherMax 22 oz + Direx 1.5 pt PDIR

38. 01.35.210.220.42.6 Staple LX fl oz/A 2004 2006

39. 1X glyphosate + 1X Staple; Palmer 0.5 inches when treated

40. Delay the arrival or spread of resistance

41. Resistance Management Practices 1.Reduce herbicide reliance (as practical) 2.Diversify MOAs; Multiple MOAs a.Multiple MOAs within a crop.

42. At PlantingTopical (1-to 4-lf cotton)Layby Directed Yellow Glyphosate + Dual Magnum or Staple MSMA or glyphosate + Diuron, Layby Pro, Suprend, or Valor *Staple will not control ALS-resistant Palmer. Sequence can be used as the glyphosate + Dual mixture. Yellow = Prowl or Treflan type products. DELAY glyphosate-resistant Palmer in RR cotton fields with LIGHT Palmer infestations*

43. Resistance Management Practices 1.Reduce herbicide reliance (as practical) 2.Diversify MOAs; Multiple MOAs a.Multiple MOAs within a crop. b.Crop rotation; different MOAs

45. Resistance Management Practices 1.Reduce herbicide reliance (as practical) 2.Diversify MOAs; Multiple MOAs a.Multiple MOAs within a crop. b.Crop rotation; different MOAs 3.Detect resistance early

46. Glyphosate-resistant Palmer amaranth: Georgia, 2005

47. Detect Resistance Early

48. More on glyphosate-resistant Palmer? From 1:30 till 2:45 in Grand Ballroom C - distribution, pollen dispersal, and management How Bad Will Glyphosate-Resistant Palmer Amaranth Become? “This Palmer amaranth stuff makes me glad I am 18 months from retirement.” Dr. Alan York

49. Weed Resistance Learning Module at National Cotton Council Web Site: http://www.cotton.org/ International Survey of Resistant Weeds * http://www.weedscience.org/in.asp Cotton Incorporated is nearing completion of a Resistance Management Bulletin Knowledge Gives Us Hope